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Ebola virus epidemic in West Africa

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Subject: West Africa, Responses to the Ebola virus epidemic in West Africa, Yambuku, 2015 Africa Cup of Nations qualification, December 2014
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Ebola virus epidemic in West Africa

The most widespread [12] though the WHO believes that this substantially understates the magnitude of the outbreak.[13][14]

This is the first Ebola outbreak to reach epidemic proportions; past outbreaks were brought under control within a few weeks. [24] On 8 April 2015, the WHO reported a total of only 30 confirmed cases,[25] and the weekly update for 29 July reported only seven new cases, the lowest total in more than a year.[26]

On 8 August 2014, the World Health Organization declared the outbreak a United Nations member countries saying, "Six months into the worst Ebola epidemic in history, the world is losing the battle to contain it."[29] In a 26 September statement, the WHO said, "The Ebola epidemic ravaging parts of West Africa is the most severe acute public health emergency seen in modern times" and the Director-General, Margaret Chan, called the outbreak "the largest, most complex and most severe we've ever seen".[30] In March 2015, the United Nations Development Group reported that due to a decrease in trade, closing of borders, flight cancellations, and foreign investment and tourism activity fuelled by stigma, the epidemic has resulted in vast economic consequences in both the affected areas and even throughout African nations that experienced low or no cases of Ebola.[31]

 On 31 July 2015, the WHO announced "an extremely promising development" in the search for an effective vaccine for Ebola disease. While the vaccine up to now shows 100% efficacy in individuals, more conclusive evidence is needed on its capacity to protect populations through what is called herd immunity.[32][33]

In August 2015, after substantial progress in reducing the scale of the epidemic, the WHO held a meeting to work out a "Comprehensive Care Plan for Ebola Survivors" and identify research needed to optimize clinical care and social well-being. Saying "the Ebola outbreak has decimated families, health systems, economies, and social structures", the WHO called the aftermath "an emergency within an emergency." Of special concern is recent research that shows some Ebola survivors experience so-called Post-Ebola Syndrome, with symptoms so severe that survivors may require medical care for months and even years.[34][35]

On 7 October 2015, all three of the most seriously affected countries recorded their first joint week without any new cases, raising hopes that the epidemic might finally be coming to an end.[36]



  Widespread outbreak
  Limited outbreak:
  Isolated cases: Sierra Leone and Guinea
  Medically evacuated cases
  Ebola-free after prior cases

Researchers generally believe that a one-year-old boy,[37] later identified as Emile Ouamouno, who died in December 2013 in the village of Meliandou, Guéckédou Prefecture, Guinea, was the index case of the current Ebola virus disease epidemic.[38][39] His mother, sister, and grandmother then became ill with similar symptoms and also died. People infected by those initial cases spread the disease to other villages.[40][41] Although Ebola represents a major public health issue in sub-Saharan Africa, no cases had ever been reported in West Africa and the early cases were diagnosed as other diseases more common to the area. Thus, the disease had several months to spread before it was recognized as Ebola.[39][40]

Monthly aggregate Ebola cases in the West Africa epidemic 2014–15
Monthly aggregate Ebola deaths

On 25 March 2014, the Guinea's Ministry of Health had reported an outbreak of Ebola virus disease in four southeastern districts, with suspected cases in the neighbouring countries of Liberia and Sierra Leone being investigated. In Guinea, a total of 86 suspected cases, including 59 deaths had been reported as of 24 March.[42] By late May, the outbreak had spread to Conakry, Guinea's capital, a city of about two million inhabitants.[42] On 28 May, the total number of cases reported had reached 281 with 186 deaths.[42]

In Liberia, the disease was reported in four counties by mid-April 2014 and cases in Liberia's capital Monrovia were reported in mid-June.[43][44] The outbreak then spread to Sierra Leone and progressed rapidly. By 17 July, the total number of suspected cases in the country stood at 442, overtaking the number in Guinea and Liberia.[45] By 20 July, additional cases of the disease had been reported in the Bo District and the first case in Freetown, Sierra Leone's capital, was reported in late July.[46][47]

As the epidemic progressed, there was a small outbreak in Nigeria that resulted in 20 cases and another in Mali with seven cases. Four other countries, Senegal, Spain, the United Kingdom and the United States of America also reported a case or cases imported from a West African country with widespread and intense transmission.

In mid-November, the WHO reported that while all cases and deaths continued to be under-reported, "there is some evidence that case incidence is no longer increasing nationally in Guinea and Liberia, but steep increases persist in Sierra Leone".[48][49][50] One year into the outbreak, the total number of cases exceeded 20,000 on 29 December 2014.

On 28 January 2015, the WHO reported that for the first time since the week ending 29 June 2014, there had been fewer than 100 new confirmed cases reported in a week in the three most-affected countries. The response to the epidemic then moved from rapidly building infrastructure to a second phase as the focus shifted to ending the epidemic.[34]

On 31 March 2015, one year since the outbreak was first reported, the total number of cases exceeded 25,000 with over 10,000 deaths according to the latest WHO report.[51] Liberia was officially declared Ebola-free on 9 May after 42 days without any further cases being recorded,[52] however new cases were reported in late June and early July after three months of being disease-free.

The 8 April 2015 WHO Ebola Situation Report stated that a total of 30 cases were reported and a 13 May report showed only nine new cases, causing a rise in hopes that the epidemic would be soon over, however the following week saw a four-fold increase in cases. Most of the new cases came from Guinea, which has been particularly unwilling to commit to safe burials. A MSN official said that peaks and valleys of cases is "normal" and to be expected.[34][53] The WHO weekly update for 29 July reported a total of only seven cases, the lowest total in more than a year.[26]

On 31 July 2015, researchers announced that a vaccine trial had been completed that appeared to give protection from the Ebola virus. The vaccine, formally called rVSV-ZEBOV but more commonly known as VSV-EBOV, has been tested and will now be used to treat known Ebola contacts.[32][33][54]

Countries that have experienced widespread transmission

Ebola outbreak in West Africa – outbreak distribution map as of 23 September 2015


On 25 March 2014, the WHO reported an outbreak of Ebola virus disease in four southeastern districts with a total of 86 suspected cases, including 59 deaths. Médecins Sans Frontières (MSF) assisted the Ministry of Health of Guinea by establishing Ebola treatment centers in the epicenter of the outbreak.[42] On 31 March, the U.S. Centers for Disease Control and Prevention (CDC) sent a five-person team to assist Guinea's Ministry of Health and the WHO as they led an international response to the Ebola outbreak.[42]

Thinking that the virus was contained, MSF closed its treatment centers in May leaving only a small skeleton staff to handle the Macenta region. However, high numbers of new cases reappeared in the region in late August.[55]

In February 2015, Guinea recorded a rise in cases for the second week in a row.[56] Health authorities said that the rise in cases was related to the fact that they "were only now gaining access to faraway villages" where violence had previously prevented them from entering.[57] On 14 February, violence erupted and an Ebola treatment center near the center of the country was destroyed. Guinea Red Cross teams said they had been attacked an average of 10 times a month over the previous year,[58] and MSF reported that acceptance of Ebola education in Guinea remained low and that an increase in violent attacks against their workers might force them to leave.[59]

Guinea's resistance to the interventions of health officials has remained greater than those of Sierra Leone and Liberia, causing concerns as the efforts to stop the epidemic progress. In mid-March there were 95 new cases and on 28 March, a 45-day "health emergency" was declared in 5 regions of the country.[59][60] On 22 May, the WHO again reported a rise in cases;[61] the rise is believed to be due to funeral transmissions.[62] On 25 May, six individuals were placed in prison isolation after they were found to be travelling with a corpse who had died of the disease.[63] On 1 June, it was reported that violent protests in a north Guinean town at the border with Guinea-Bissau had caused the Red Cross to withdraw workers.[64]

In late June the WHO reported, “Weekly case incidence has stalled at between 20 and 27 cases since the end of May, whilst cases continue to arise from unknown sources of infection, and to be detected only after post-mortem testing of community deaths.”[65] On 29 July, a sharp decline in cases was reported,[26] with only one case left by the end of the week.[66] The number of cases plateaued at 1 or 2 cases per week after the beginning of August. No new cases had occurred since 16 September[67] but on 16 October, two new cases were detected, one of them in Forecariah.[68] On 28 October a further three cases were reported in the Forecariah district by the WHO.[12] On 1 November, a newborn baby tested positive for the virus, even though both parents tested negative.[69]

Sierra Leone

Kenema Hospital, Sierra Leone

The first person reported infected in the spread to Sierra Leone was a tribal healer who had been treating Ebola patients from across the nearby border with Guinea and died on 26 May 2014. According to tribal tradition, her body was washed for burial and this appears to have led to infections in women from neighbouring towns.[70] On 11 June, Sierra Leone shut its borders for trade with Guinea and Liberia and closed some schools in an attempt to slow the spread of the virus.[71] On 30 July, the government began to deploy troops to enforce quarantines.[72] By 15 October, the last district in Sierra Leone untouched by the disease had declared Ebola cases.[73]

During the first week of November, it was reported that the situation was "getting worse" due to intense transmission in Freetown as a contributing factor. According to the Disaster Emergency Committee, food shortages resulting from aggressive quarantines were making the situation worse.[74] On 4 November, it was reported that thousands violated quarantine in search for food in the town of Kenema.[75] With the number of cases continuing to increase, a MSF coordinator reported the situation in Sierra Leone as "catastrophic", saying: "There are several villages and communities that have been basically wiped out... Whole communities have disappeared but many of them are not in the statistics."[76] In mid-November the WHO reported that, while there was some evidence that cases were no longer increasing in Guinea and Liberia, steep increases persisted in Sierra Leone.[48] Although the international community had responded to the emergency by building and equipping treatment centres, they were not able to function effectively because of lack of staff, poor coordination, government mismanagement and inefficiency.[77]

Ebola crisis: More UK aid arrives in Sierra Leone

On 9 December, news reports described the discovery of "a grim scene": piles of bodies, overwhelmed medical personnel and exhausted burial teams in the remote Eastern Kono District.[78] On 15 December, the CDC indicated that their main concern was Sierra Leone where the epidemic had given no evidence of halting and cases continued to rise exponentially; during the second week of December Sierra Leone reported nearly 400 cases, more than three times the number of cases reported by Guinea and Liberia combined. According to the CDC, "the risk we face now [is] that Ebola will simmer along, become endemic and be a problem for Africa and the world, for years to come."[79] On 17 December, President Koroma launched "Operation Western Area Surge" and workers went door-to-door in the capital city looking for possible cases.[80][81] The operation led to a surge in the number of cases, with 403 new cases reported between 14 and 17 December.[80][82]

According to the 21 January 2015 WHO Situation Report, case incidence was rapidly decreasing in Sierra Leone,[83][84] but in February and March it was reported that there was a rise in the number of cases[85][86] [87][88] A 5 April WHO report again disclosed a downward trend[89] and the WHO weekly update for 29 July reported a total of only three new cases, the lowest total in more than a year.[26] On 17 August, the country had its first week with no new cases,[90] and one week later the last patients were released.[91] However, a new case was reported on 1 September when a patient from Sella Kafta village in Kambia District tested positive for the disease after her death.[92] Eventually, her case resulted in three more cases among her contacts. [93]

On 14 September, the National Ebola Response Center confirmed the death of a 16-year-old in a village in the Bombali district.[94] It is suspected that she contracted the disease from the semen of an Ebola survivor who was discharged in March 2015.[95] On 28 September, a new 42-day countdown began to declare the country Ebola-free.[96]


An Ebola treatment unit in Liberia

In Liberia, the disease was reported in both Lofa and Nimba counties in late March 2014.[97] On 27 July, Ellen Johnson Sirleaf, the Liberian president, announced that Liberia would close its borders, with the exception of a few crossing points such as the airport, where screening centres would be established.[98] Schools and universities were closed,[99][100] and the worst-affected areas in the country were placed under quarantine.[101]

With only 50 physicians in the entire country—one for every 70,000 Liberians—Liberia already faced a health crisis even before the outbreak.[102] In September the US CDC reported that some hospitals had been abandoned while those still functioning lacked basic facilities and supplies.[103] In October, the Liberian ambassador in Washington was reported as saying that he feared that his country may be "close to collapse".[102] By 24 October, all of the 15 Liberian districts had reported Ebola cases.[104][105]

In November the rate of new infections in Liberia appeared to be declining and the state of emergency was lifted. The drop in cases was believed to be related to an integrated strategy combining isolation and treatment with community behaviour change including safe burial practices, case finding and contact tracing.[106][107]

In January 2015, the MSF field coordinator reported that Liberia was down to only five confirmed cases.[108] In March, after two weeks of not reporting any new cases, three new cases were confirmed.[109] On 8 April, a new health minister was named in an effort to end Ebola in Liberia. On 26 April, Doctors Without Borders handed ELWA – 3, an Ebola treatment facility, back to the government of Liberia.[110] On 30 April, the U.S. shut down a special Ebola treatment unit in Liberia.[111] The last known case of Ebola died on 27 March,[112] and the country was officially declared Ebola-free on 9 May after 42 days without any further cases being recorded. The WHO congratulated Liberia saying, "Reaching this milestone is a testament to the strong leadership and coordination of Liberian President Ellen Johnson Sirleaf and the Liberian Government, the determination and vigilance of Liberian communities, the extensive support of global partners, and the tireless and heroic work of local and international health teams."[52] As of May 2015, the country remained on high alert against recurrence of the disease.[113][114][115]

After three months with no new reports of cases, on 29 June Liberia reported that the body of a 17-year-old boy who had been treated for malaria tested positive for Ebola. The WHO said the boy had been in close contact with at least 200[116] people, who they were following, and that "the case reportedly had no recent history of travel, contact with visitors from affected areas, or funeral attendance." A second case was confirmed on 1 July.[117][118] After a third new case was confirmed on 2 July and it was discovered that all three new cases had shared a meal of dog meat, researchers looked at the possibility that the dog meat may have been involved in the transfer of the virus.[119][120] However, testing of the dog's remains were negative for the Ebola virus.[121] By 9 July two more cases were discovered, bringing the total number of new cases to five, all from the same area.[122] On 14 July a woman died due to the virus in the county of Montserrado, bringing the total of new cases to 6 people.[123] On 20 July, the last patients were discharged,[124] and on 3 September, Liberia was declared Ebola-free again.[125]

West African countries with successfully contained spread


In March 2014, the Senegal Ministry of Interior closed its southern border with Guinea,[126] but on 29 August the Senegal health minister announced Senegal's first case, a university student from Guinea who was being treated in a Dakar hospital.[127] The case was a native of Guinea who had traveled to Dakar, arriving on 20 August. On 23 August, he sought medical care for symptoms including fever, diarrhoea, and vomiting. He received treatment for malaria, but did not improve and left the facility. Still experiencing the same symptoms, on 26 August he was referred to a specialized facility for infectious diseases, and was subsequently hospitalized.[127]

On 28 August 2014, authorities in Guinea issued an alert informing medical services in Guinea and neighbouring countries that a person who had been in close contact with an Ebola infected patient had escaped their surveillance system. The alert prompted testing for Ebola at the Dakar laboratory, and the positive result launched an investigation and triggered urgent contact tracing.[127] On 10 September, it was reported that the student had recovered but health officials would continue to monitor his contacts for 21 days.[128] No further cases were reported.[129] and on 17 October, the WHO officially declared that the outbreak in Senegal had ended.[104]

The WHO have officially commended the Senegalese government, and in particular the President Macky Sall and the Minister of Health Dr Awa Coll-Seck, for their response in quickly isolating the patient and tracing and following up 74 contacts, as well as for their public awareness campaign. This acknowledgement was also extended to MSF and the CDC for their assistance.[130]


The first case in Nigeria was a Liberian-American, who flew from Liberia to Nigeria's most populated city of Lagos on 20 July 2014. On 6 August 2014, the Nigerian health minister told reporters that one of the nurses that attended to the Liberian died from the disease. Five newly confirmed cases were being treated at an isolation ward.[131]

On 22 September 2014, the Nigeria health ministry announced, "As of today, there is no case of Ebola in Nigeria." According to the WHO, 20 cases and 8 deaths had been confirmed, including the imported case, who also died. Four of the dead were health care workers who had cared for the index case.[132]

The WHO's representative in Nigeria officially declared Nigeria to be Ebola free on 20 October after no new active cases were reported in the follow up contacts, stating it was a "spectacular success story".[133]


Malian regions with Ebola cases (Kayes and Bamako), as of November 2014

On 23 October 2014, the first case of Ebola disease in Mali was confirmed in the city of Kayes; a two-year-old girl who had arrived with a family group from Guinea. Her father had worked for the Red Cross in Guinea and had also worked in a private health clinic; he died earlier in the month, likely from an Ebola infection he had contracted in the private clinic. It was later established that a number of family members had also died of Ebola. A family group returned to Mali after the father's funeral via public bus and taxi, a journey of more than 1,200 kilometres (750 mi). On 23 October, the girl tested positive for Ebola but died the next day.[134][135] All contacts were followed for 21 days, with no further spread of the disease reported.[136]

On 12 November 2014, Mali reported deaths from Ebola in an outbreak unconnected with the first case in Kayes. The first probable case was an imam who had fallen ill on 17 October in Guinea and was transferred to the Pasteur Clinic in Mali's capital city Bamako for treatment. He was treated for kidney failure but was not tested for Ebola; he died on 27 October and his body was returned to Guinea for burial.[137] A nurse and a doctor who had treated the imam subsequently fell ill with Ebola and died.[138][139] The next three cases were related to the imam as well: a man who had visited the imam while he was in hospital, his wife, and his son. On 22 November, the final case related to the imam was reported: a friend of the Pasteur Clinic nurse who had died from the Ebola virus.[140] On 12 December, the last case in treatment recovered and was discharged, "so there are no more people sick with Ebola in Mali", according to a Ministry of Health source.[141] On 16 December, Mali released the final 13 individuals who were being quarantined[142] and 24 days later (18 January 2015) without new cases the country was declared Ebola-free.[8]

Countries with limited local cases

United Kingdom

On 29 December 2014, Pauline Cafferkey, a British aid worker who had just returned to Glasgow from Sierra Leone was diagnosed with Ebola.[143] She was treated and declared to be free of infection and released from hospital on 24 January 2015.[144][145] On 8 October, she was readmitted for complications caused by the virus[146] and was in "serious" condition according to a hospital report. On 14 October her condition was listed as "critical"[147] and 58 individuals were being monitored and 25 received an experimental vaccination, due to close contact.[148][149] On 21 October, it was reported that she had been diagnosed with meningitis caused by the virus persisting in her brain.[150]


On 12 May 2015, it was reported that a nurse who had been working in Sierra Leone had been diagnosed with Ebola after returning home to the Italian island of Sardinia. He was treated at Spallanzani Hospital, the national reference center for Ebola patients.[151] On 10 June it was reported that he had recovered and was disease-free and he was released from hospital.[152]


On 5 August 2014, the Brothers Hospitallers of St. John of God confirmed that Brother Miguel Pajares, who had been volunteering in Liberia, had become infected. He was evacuated to Spain and died on 12 August.[153] On 21 September it was announced that Brother Manuel García Viejo, another Spanish citizen who was medical director at the San Juan de Dios Hospital in Lunsar, had been evacuated to Spain from Sierra Leone after being infected with the virus. His death was announced on 25 September.[154]

In October 2014, a nursing assistant, Teresa Romero, who had cared for these patients became unwell and on 6 October tested positive for Ebola,[155][156] making this the first confirmed case of Ebola transmission outside of Africa. On 19 October, it was reported that Romero had recovered, and on 2 December the WHO declared Spain Ebola-free following the passage of 42 days since Teresa Romero was found to be cured.[157]

United States

On 30 September 2014, the United States Centers for Disease Control and Prevention (CDC) declared its first case of Ebola virus disease. The CDC disclosed that Thomas Eric Duncan became infected in Liberia and traveled to Texas on 20 September. On 26 September he fell ill and sought medical treatment but was sent home with antibiotics. He returned to the hospital by ambulance on 28 September and was placed in isolation and tested for Ebola.[158][159] Thomas Duncan died on 8 October.[160] Two additional cases stemmed from Thomas Eric Duncan, when two nurses that had treated him tested positive for Ebola on October 10 and 14[161][162] and ended when they were declared Ebola free on October 24 and 22, respectively.[163][164]

A fourth case of Ebola was identified on 23 October 2014 when a physician who had treated Ebola patients in West Africa, himself tested positive for Ebola.[165] This case had no relation to the cases originating from Thomas Eric Duncan. He recovered and was released from hospital on 11 November.[166]

Countries with medically evacuated cases

A number of people who had become infected with Ebola were medically evacuated for treatment in isolation wards in Europe or the US. They were mostly health workers with one of the NGOs in West Africa. With the exception of a single isolated case in Spain, no secondary infections occurred as a result of the medical evacuations. The United States accepted four evacuees, three were flown to Germany,[167][168][169] and France received two.[170][171] Italy,[172] the Netherlands,[173] Norway,[174][175] Switzerland,[176] and the United Kingdom received one patient each.[177]

Unrelated outbreak in the Democratic Republic of the Congo

In August 2014, the WHO reported an outbreak of Ebola virus in the Boende District, part of the northern Équateur province of the Democratic Republic of the Congo (DRC), where 13 people were reported to have died of Ebola-like symptoms.[178] Genetic sequencing revealed that this outbreak was the Zaire Ebola species, which is indigenous to the DRC; there have been seven previous Ebola outbreaks in the country since 1976. The virology results and epidemiological findings indicate no connection to the epidemic in West Africa.[178][179]

The index case was initially reported to have been a woman from Ikanamongo Village, who became ill with the symptoms of Ebola after she had butchered a bush animal.[178][180] However more recent findings suggested that there may have been several previous cases, and it was reported that the pigs in the village may have been infected with Ebola some time before the first human case occurred.[181] The WHO declared the outbreak over on 21 November 2014, with a total of 66 cases with 49 deaths.[182][183]


Ebola virus particles using electron micrograph

Ebola virus disease is caused by four of five viruses classified in the genus Ebolavirus. Of the four disease-causing viruses, Ebola virus (formerly and often still called the Zaire virus), is the most dangerous and is the species responsible for the ongoing epidemic in West Africa.[184][185] Since the discovery of the viruses in 1976 when outbreaks occurred in Sudan and the Democratic Republic of Congo (then called Zaire), Ebola virus disease has been confined to areas in Central Africa, where it is endemic. With the current outbreak, it was initially thought that a new species endemic to Guinea might be the cause, rather than being imported from central to West Africa.[39] However, further studies have shown that the current outbreak is likely caused by an Ebola virus lineage that has spread from Central Africa via an animal host within the last decade, with the first viral transfer to humans in Guinea.[184][186]

In a study done by Tulane University, the Broad Institute and Harvard University, in partnership with the Sierra Leone Ministry of Health and Sanitation, researchers may have provided information about the origin and transmission of the Ebola virus that sets this outbreak apart from previous outbreaks. For this study, 99 Ebola virus genomes were collected and sequenced from 78 patients diagnosed with the Ebola virus during the first 24 days of the outbreak in Sierra Leone. From the resulting sequences, and three previously published sequences from Guinea, the team found 341 genetic changes that make the outbreak distinct from previous outbreaks. It is still unclear whether these differences are related to the severity of the current situation.[184] Five members of the research team became ill and died from Ebola before the study was published in August 2014.[184]

Ebola virus particles

In January 2015, researchers in Guinea reported mutations in the virus samples that they were looking at. They reported: "We've now seen several cases that don't have any symptoms at all, asymptomatic cases. These people may be the people who can spread the virus better, but we still don't know that yet. A virus can change itself to less deadly, but more contagious and that's something we are afraid of." Also, while extremely unlikely, researchers remain concerned that the virus could morph into an airborne disease given the time.[187]

The ongoing genome studies have provided valuable information in the study of the Ebola virus. In a report released in August 2014, researchers tracked the spread of Ebola in Sierra Leone from the group first infected, the 13 women who had attended the funeral of a traditional healer where they contracted the disease, giving a unique opportunity to track how the virus has changed. This tracking provided "the first time that the real evolution of the Ebola virus can be observed in humans.” The research showed that the outbreak in Sierra Leone was sparked by at least two distinct viruses introduced from Guinea at about the same time. It is not clear whether the traditional healer was infected with both variants, or if perhaps one of the women attending the funeral was independently infected. As the Sierra Leone epidemic progressed, one virus lineage disappeared from patient samples, while a third lineage appeared. At the time the study was released it was thought that the genome was changing fairly rapidly, raising concerns related to diagnostic testing, vaccines, and the effectiveness of medications such as the drug ZMapp.[188][189] However, later research showed that the virus had in fact mutated at a significantly slower rate than had been reported at that time. An international study done by Public Health England and released in June 2015 found that the rate of mutations was only slightly higher than the rate seen in previous outbreaks "...which is reassuring to public health experts around the world."[190]

On 3 June 2015, the sequencing data of the virus was released[191] and on 24 June, a report was issued that identified three distinct viral lineages that had circulated in Guinea in 2014.[192]


Animal to human transmission

The life cycles of the Ebolavirus

It is not entirely clear how an Ebola outbreak starts.[193] The initial infection is believed to occur after an Ebola virus is transmitted to a human by contact with an infected animal's body fluids. Evidence strongly implicates bats as the reservoir hosts for ebolaviruses. Bats drop partially eaten fruits and pulp, then land mammals such as gorillas and duikers feed on these fallen fruits. This chain of events forms a possible indirect means of transmission from the natural host to animal populations.[194] As primates in the area were not found to be infected and fruit bats do not live near the location of the initial zoonotic transmission event in Meliandou, Guinea it is suspected that the index case occurred after a child had contact with an insectivorous bat from a colony of Angolan free-tailed bats near the village.[195]

Human to human transmission

Based on a limited number of studies it is believed that human-to-human transmission occurs only via direct contact with blood or bodily fluids from an infected person who is showing signs of infection or by contact with objects recently contaminated by an actively ill infected person.[196] Other possible methods of transmission are currently being studied.[197] The time interval from infection with the virus to onset of symptoms is two to twenty-one days. Because dead bodies are still infectious, the handling of the bodies of Ebola victims can only be done while observing proper barrier/ separation procedures.[198] One study suggested that the virus can live up to 7 days in a deceased individual.[199][200][201]

Airborne transmission

Airborne transmission has not been documented during Ebola outbreaks, however in February 2015 a group of researchers published a paper suggesting, "it is very likely that at least some degree of Ebola virus transmission currently occurs via infectious aerosols". Commenting on the study, an infectious disease specialist said that while the study raised issues "it would be rare; as the study points out, it has never been demonstrated in humans."[202]

Sexual transmission

According to information distributed by the WHO in September 2014, "No formal evidence exists of sexual transmission, but sexual transmission from convalescent patients cannot be ruled out. There is evidence that live Ebola virus can be isolated in seminal fluids of convalescent men for 82 days after onset of symptoms. Evidence is not available yet beyond 82 days."[200] In April 2015, following a report that the Ebola virus had been detected in a semen sample six months after a man's recovery, the WHO issued a statement saying, "For greater security and prevention of other sexually transmitted infections, Ebola survivors should consider correct and consistent use of condoms for all sexual acts beyond three months until more information is available."[203][204]

The WHO based their new recommendations on a March 2015 case in which a Liberian woman who had no contact with the disease other than having had unprotected sex with a man who had had the disease in October 2014 was diagnosed with Ebola. While no evidence of the virus was found in his blood, his semen revealed Ebola virus RNA closely matching the strain that infected the woman, however "doctors don’t know if there was any fully formed (and therefore infectious) virus in the guy’s semen." It is known that a male's testes are protected from the body's immune system in order to protect the developing sperm, and it is thought that it may be that this same protection may allow the Ebola virus to survive in the male testes for an unknown time.[205]

On 14 September 2015, the body of a girl that had died in Sierra Leone tested positive for Ebola[94] and it was suspected that she may have contracted the disease from the semen of an Ebola survivor who was discharged in March 2015.[95] According to some news reports, a new study to be published in the New England Journal of Medicine indicates the possibility that the virus may remain in the semen of survivors for up to six months.[206]

Containment difficulties

One of the primary reasons for spread is the poorly-functioning health systems in the part of Africa where the disease occurs.[207] The risk of transmission is increased among those caring for people infected. Recommended measures when caring for those who are infected include medical isolation via the proper use of boots, gowns, gloves, masks and goggles, and sterilizing equipment and surfaces.[193]

One of the biggest dangers of infection faced by medical staff requires their learning how to properly suit up and remove personal protective equipment. Full training for wearing protective body clothing can take 10 to 14 days.[208] Even with proper isolation equipment available, working conditions such as lack of running water, climate control, and flooring have made direct care difficult. Two American health workers who contracted the disease and later recovered said that to the best of their knowledge their team of workers had been following "to the letter all of the protocols for safety that were developed by the CDC and WHO", including a full body coverall, several layers of gloves, and face protection including goggles. One of the two, a physician, had worked with patients, but the other was assisting workers to get in and out of their protective gear, while wearing protective gear herself.[209]

Difficulties in attempting to halt transmission have also included the multiple disease outbreaks across country borders.[210] Dr Peter Piot, the scientist who co-discovered the Ebola virus, has stated that the present outbreak is not following its usual linear patterns as mapped out in previous outbreaks. This time the virus is "hopping" all over the West African epidemic region.[55] Furthermore, past epidemics have occurred in remote regions, but this outbreak has spread to large urban areas, which has increased the number of contacts an infected person may have and has made transmission harder to track and break.[211]

Containment and control

Nigerian doctors receive training in how to use protective clothing by the World Health Organization.

In August 2014, the WHO published a road map of the steps required to bring the epidemic under control and to prevent further transmission of the disease within West Africa; the coordinated international response is working to realise this plan.[212] Key elements required to prevent transmission are contact tracing and follow-up as well as social mobilisation and public awareness.

Surveillance and contact tracing

Contact tracing is an essential method of preventing the spread of the disease. This requires effective community surveillance so that a possible case of Ebola can be registered and accurately diagnosed as soon as possible, and subsequently finding everyone who has had close contact with the case and tracking them for 21 days. However, this requires careful record-keeping by properly trained and equipped staff.[213] WHO Assistant Director-General for Global Health Security, Keiji Fukuda, said on 3 September, "We don't have enough health workers, doctors, nurses, drivers, and contact tracers to handle the increasing number of cases."[214] There is a massive ongoing effort to train volunteers and health workers, sponsored by USAID.[215] According to WHO reports, 25,926 contacts from Guinea, 35,183 from Liberia and 104,454 from Sierra Leone were listed and being traced as of 23 November 2014.[49]

Community awareness

To reduce the spread, the Plan International in Guinea, "The poor living conditions and lack of water and sanitation in most districts of Conakry pose a serious risk that the epidemic escalates into a crisis. People do not think to wash their hands when they do not have enough water to drink."[218]

A number of organisations enrolled local people to conduct public awareness campaigns among the communities in West Africa.[219] "...what we mean by social mobilization is to try to convey the right messages, in terms of prevention measures, adapted to the local context – adapted to the cultural practices in a specific area,” said Vincent Martin, FAO’s representative in Senegal.[220]

Denial in some affected countries also made containment efforts difficult.[221] Language barriers and the appearance of medical teams in protective suits sometimes increased fears of the virus.[222] In Liberia, a mob attacked an Ebola isolation centre, stealing equipment and "freeing" patients while shouting "There's no Ebola."[223] Red Cross staff were forced to suspend operations in southeast Guinea after they were threatened by a group of men armed with knives.[224] In September in the town of Womey in Guinea, suspicious inhabitants wielding machetes murdered at least eight aid workers and dumped their bodies in a latrine.[225]

An August 2014 study found that nearly two thirds of Ebola cases in Guinea were believed to be due to burial practices including [229]

Travel restrictions and quarantines

A quarantine travel pass for people providing help to people who are infected with Ebola

There was serious concern that the disease would spread further within West Africa or elsewhere in the world.

West Africa

On 8 August 2014, a cordon sanitaire, a disease-fighting practice that forcibly isolates affected regions, was established in the triangular area where Guinea, Liberia, and Sierra Leone are separated only by porous borders and where 70 percent of the known cases had been found.[230] This was subsequently replaced by a series of simple checkpoints for hand-washing and measuring body temperature on major roads throughout the region, manned either by local volunteers or by the military.[231][232]


Many countries considered imposing restrictions on travel to or from the region. On 2 September 2014, WHO Director-General Margaret Chan advised against this, saying that they were not justified and that they prevent medical experts from entering the affected areas and that they were "marginalizing the affected population and potentially worsening the crisis". UN officials working on the ground also criticized the travel restrictions, saying the solution is "not in travel restrictions but in ensuring that effective preventive and curative health measures are put in place".[22] MSF also spoke out against the closure of international borders, called them "another layer of collective irresponsibility" and added, "The international community must ensure that those who try to contain the outbreak can enter and leave the affected countries if need be."[29]

As of February 2015, countries still maintaining entry restrictions for Ebola affected countries were Antigua and Barbuda, Australia, Bahrain, Belize, Botswana, Brazil, Cameroon, Cape Verde, Cayman Islands, Central African Republic, Chad, Ivory Coast, Dominican Republic, Equatorial Guinea, Gabon, Gambia, Guyana, Haiti, India, Iraq, Jamaica, Kenya, Maldives, Mauritius, Mongolia, Oman, Panama, Rwanda, Sao Tome and Principe, Saudi Arabia, Senegal, Seychelles, Singapore, South Africa, Sri Lanka, Saint Kitts and Nevis, Suriname, Trinidad and Tobago and the United States.[233]

Returning health workers

There was concern that people returning from affected countries, such as health workers and reporters, may have been incubating the disease and become infectious after arriving. A number of agencies issued guidelines for returning workers. Examples include the CDC,[234] MSF,[235] Public Health England,[236] and Public Health Ontario.[237] They generally recommended a risk assessment based on the likelihood of exposure with advisories recommending that people in the low risk category self-monitor for 21 days for symptoms that might indicate Ebola, and outlined more stringent requirements for those at higher risk.


Practising taking blood in Ebola safety suits

No proven Ebola virus-specific treatment presently exists,[238] however measures can be taken to improve a patient's chances of survival.[239] Ebola symptoms may begin as early as two days or as long as 21 days after one is exposed to the virus. They usually begin with a sudden influenza-like stage characterized by feeling tired, fever, and pain in the muscles and joints. Later symptoms may include headache, nausea, and abdominal pain. This is often followed by severe vomiting and diarrhoea.[240] In past outbreaks it has been noted that some patients may experience the loss of blood through bleeding internally and/or externally, however data published in October 2014 showed that bleeding had been a rare symptom in this outbreak.[241] Another study published in October 2014 suggested that a person's genetic makeup may play a major role in determining how an infected person's body reacts to the disease, with some infected people experiencing mild or no symptoms while some progress to a very severe stage that includes massive bleeding.[242]

Without fluid replacement, such extreme loss of fluids leads to dehydration, which may lead to hypovolaemic shock—a condition in which there isn't enough blood for the heart to pump through the body. If a patient is alert and is not vomiting, oral rehydration fluids may be given, but patients who are vomiting or are delirious must be hydrated with intravenous therapy (IV). However, administration of intravenous fluids is difficult in the African environment. Inserting an IV needle while wearing three pairs of gloves and goggles that may be fogged is difficult, and once in place, the IV site and line must be constantly monitored. Without sufficient staff to care for patients, needles may become dislodged or pulled out by a delirious patient. A patient's electrolytes must be closely monitored to determine correct fluid administration, and many areas did not have access to laboratory services.[243]

According to the WHO, the main reason that most patients in American and European hospitals survived was due to the use of IV fluids along with constant measuring of blood chemistry. However, at the height of the epidemic facilities had little to offer in terms of equipment, staffing, and laboratory services. Treatment centers were overflowing with patients while others waited to be admitted and dead patients were so numerous that it was difficult to arrange for safe burials. Based on many years of experience in Africa and several months of experience working with the present epidemic, MSF took a conservative approach. While using IV treatment for as many patients as they could manage, they argued that improperly managed IV treatment is not helpful and may even kill a patient when not properly managed. They also said that they were concerned about further risk to already overworked staff.[243] While experts have studied the mortality rates of different treatment settings, given the wide differences in variables that affect outcome adequate information has not yet been gathered to make a definitive statement about what may constitute the optimal care in the West African setting.[244]Paul Farmer of Partners in Health, an NGO that as of January 2015 had only recently begun to treat Ebola patients, strongly supported IV therapy for all Ebola patients stating, “What if the fatality rate isn’t the virulence of disease but the mediocrity of the medical delivery?" Farmer suggested that every treatment facility should have a team that specializes in inserting IVs, or better yet, peripherally inserted central catheter (PICC) lines.[243]


Ebola virus disease has a high case fatality rate (CFR-risk of death in those infected), which in past outbreaks has varied between 25 percent and 90 percent of those who have contracted the disease. The previous average case fatality rate is about 50%, however it is known that the Zaire species, which is responsible for the current outbreak, carries a higher death rate.[245] The current epidemic has caused significant mortality, with reported case fatality rates of up to 70%.[3][4][5][6] Care settings that have access to medical expertise may increase survival by providing maintenance of hydration, circulatory volume, and blood pressure.[241]

The disease affects males and females equally and the majority of those that contract Ebola disease are between 15 and 45 years of age.[3] For those over 45 years of age, a fatal outcome has been more likely in the current epidemic, as has also been noted in past outbreaks.[241] Only rarely do pregnant women survive. A midwife who works with MSF in a Sierra Leone treatment center states that she knew of "no reported cases of pregnant mothers and unborn babies surviving Ebola in Sierra Leone."[246] In September 2015 the WHO organization issued pregnancy guidance information entitled, "Interim Guidance on Ebola Virus Disease in Pregnancy."[247][248]

It has been suggested that the loss of human life was not limited to Ebola victims alone. Many hospitals had to shut down leaving people with other medical needs without care. A spokesperson for the UK-based health foundation the Wellcome Trust said in October 2014 that "the additional death toll from malaria and other diseases [is] likely to exceed that of the outbreak itself".[20] Doctor Paul Farmer stated "Most of Ebola's victims may well be dying from other causes: women in childbirth, children from diarrhoea, people in road accidents or from trauma of other sorts."[21] As the epidemic began to come to a close in 2015, a report from Sierra Leone showed that the fear and mistrust of hospitals generated by the epidemic had resulted in giving birth at health centres falling by 11%, and those receiving care before or after birth falling by about a fifth. Consequently, the deaths of women during or just after childbirth rose by almost a third and those of newborns by a quarter between May 2014 and April 2015 compared with the previous year.[249]

Post-Ebola Syndrome

As of May 2015, there are at least 10,000 people who have survived infection from the Ebola virus; some survivors have reported lingering health effects. In early November a WHO consultant reported, “Many of the survivors are discharged with the so-called Post-Ebola Syndrome. We want to ascertain whether these medical conditions are due to the disease itself, the treatment given or chlorine used during disinfection of the patients. This is a new area for research; little is known about the post-Ebola symptoms.”[250][251] In June 2015, a five-year study was begun in Liberia on the effects of post-Ebola syndrome.[252][253]


An observational study done roughly 29 months after the outbreak on survivors of the 2007 Bundibugyo Ebola virus outbreak in Uganda found that long-term sequelae (consequences) persisted for more than two years after Ebola virus disease. Symptoms included eye pain, blurred vision, hearing loss, difficulty swallowing, difficulty sleeping, arthralgias, memory loss or confusion, and "various constitutional symptoms controlling for age and sex."[254]

In February 2015, a Sierra Leone physician said about half of the recovered patients she saw reported declining health and that she had seen survivors go blind.[255][256] In May 2015 a senior consultant to the WHO said that the reports of eye problems were especially concerning because "there are hardly any ophthalmologists in West Africa, and only they have the skills and equipment to diagnose conditions like uveitis that affect the inner chambers of the eye."[35]

A study published in May 2015 discussed the case of Ian Crozier, a Zimbabwe-born physician and American citizen who became infected with Ebola while he was working at an Ebola treatment center in Sierra Leone. He was transported to the US and was successfully treated at Emory University Hospital. However, after discharge Crozier began to experience symptoms including low back pain, bilateral enthesitis of the Achilles tendon, paresthesias involving his lower legs, and eye pain, which was diagnosed as uveitis. His eye condition worsened and a specimen of aqueous humor was obtained from his eye which tested positive for Ebola. The authors of the study concluded "Further studies to investigate the mechanisms responsible for the ocular persistence of Ebola and the possible presence of the virus in other immune-privileged sites (e.g., in the central nervous system, gonads, and articular cartilage) are warranted." The authors also noted that 40% of participants in a survey of 85 Ebola survivors in Sierra Leone reported having “eye problems", though the incidence of actual uveitis was unknown.[257]

The medical director of a hospital in Liberia reported that he was seeing health problems in patients who had been in recovery for as long as nine months. Problems he was seeing included chronic pain, sometimes so severe that walking was difficult; eye problems, including uveitis; and headaches as the most common physical symptoms. “They’re still very severe and impacting their life every day. These patients will need medical care for months and maybe years." A physician from the Kenema hospital in Sierra Leone reported similar health difficulties.[35]

In December 2014, a British aid worker who had just returned to Glasgow from Sierra Leone was diagnosed with Ebola. She was treated with survivors' blood plasma and experimental drugs and declared free of disease in January 2015. However, in October 2015 she became ill and was again admitted for treatment. According to a news report, on 21 October she was diagnosed with meningitis related to the Ebola virus disease which it had been thought she had been successfully treated for.[150]

Level of care

WHO workers gear up to go into Ebola isolation ward in Lagos, Nigeria – 2014.

In June 2014 it was reported that local authorities did not have resources to contain the disease, with health centres closing and hospitals becoming overwhelmed.[258] There were also reports that adequate personal protection equipment was not being provided for medical personnel.[259] The Director-General of MSF said, "Countries affected to date simply do not have the capacity to manage an outbreak of this size and complexity on their own. I urge the international community to provide this support on the most urgent basis possible."[210]

In late August, [260]

By September, treatment for Ebola patients had become unavailable in some areas. Speaking on 12 September, WHO Director-General Margaret Chan said, "In the three hardest hit countries, Guinea, Liberia and Sierra Leone, the number of new cases is moving far faster than the capacity to manage them in the Ebola-specific treatment centers. Today, there is not one single bed available for the treatment of an Ebola patient in the entire country of Liberia."[261] According to a WHO report released on 19 September, Sierra Leone was currently meeting only 35% of its need for patient beds, and Liberia was meeting only 20% of its need.[262] The WHO set a goal to isolate and treat 100% of Ebola cases and provide safe burials by 1 January 2015.

In early December, the WHO reported that at a national level there were a sufficient number of beds in treatment facilities to treat and isolate all reported Ebola cases, although the uneven distribution of cases was resulting in serious shortfalls in some areas. Similarly, all affected countries had sufficient and widespread capacity to bury all reported deaths; however, because not all deaths are reported, it was possible that some areas still had insufficient burial capacity. They reported that every district now had access to a laboratory to confirm cases of Ebola within 24 hours from sample collection, and that all three countries had reported that more than 80% of registered contacts associated with known cases of EVD were being traced, although contact tracing was still a challenge in areas of intense transmission and in areas of community resistance.[23]

Healthcare settings

Ebola treatment centre built by the UK in Kerry Town, Sierra Leone, in 2014

A number of triage area, and low- and high-risk care wards. For staff, there are areas for preparation and decontamination. An important part of each centre is an arrangement for safe burial or cremation of bodies, required to prevent further infection.[263][264] In January 2015, a new treatment and research center was built by Rusal and Russia in the city of Kindia in Guinea. It is one of the most modern medical centers in Guinea.[265][266] Also in January, MSF admitted its first patients to a new treatment centre in Kissy, an Ebola hotspot on the outskirts of Freetown, Sierra Leone. The center has a maternity unit for pregnant women with the virus.[267][268]

Although the WHO does not advise caring for Ebola patients at home, in some cases it became a necessity when no hospital treatment beds were available. For those being treated at home, the WHO advised informing the local public health authority and acquiring appropriate training and equipment.[269][270] UNICEF, USAID and the NGO Samaritan's Purse began to take measures to provide support for families that were forced to care for patients at home by supplying caregiver kits intended for interim home-based interventions. The kits included protective clothing, hydration items, medicines, and disinfectant, among other items.[271][272] Even where hospital beds were available, it was debated whether conventional hospitals are the best place to care for Ebola patients, as the risk of spreading the infection is high.[273] In October the WHO and non-profit partners launched a program in Liberia to move infected people out of their homes into ad hoc centres that could provide rudimentary care.[274]

Protective clothing

Examining equipment

The Ebola epidemic caused an increasing demand in protective clothing. A full set of protective clothing includes a suit, goggles, mask, socks and boots, and an apron. Boots and aprons can be disinfected and reused, but everything else must be destroyed. Health workers change garments frequently, discarding gear that has barely been used. This not only uses a great deal of time but also exposes them to the virus because for health care workers wearing protective clothing, one of the most dangerous times for catching Ebola is while suits are being removed.[275]

The protective clothing set that MSF uses cost about $75 apiece. Staff who have returned from deployments to West Africa say the clothing is so heavy that it can be worn for only about 40 minutes at a stretch. A physician working in Sierra Leone has said, "After about 30 or 40 minutes, your goggles have fogged up; your socks are completely drenched in sweat. You're just walking in water in your boots. And at that point, you have to exit for your own safety...Here it takes 20–25 minutes to take off a protective suit and must be done with two trained supervisors who watch every step in a military manner to ensure no mistakes are made, because a slip up can easily occur and of course can be fatal."[276][277] By October there were reports that protective outfits were beginning to be in short supply and manufacturers began to increase their production,[278] but the need to find better types of suits has also been raised.[279]

USAID published an open competitive bidding for proposals that address the challenge of developing "... new practical and cost-effective solutions to improve infection treatment and control that can be rapidly deployed; 1) to help health care workers provide better care and 2) transform our ability to combat Ebola".[280][281][282] On 12 December 2014, USAID announced the result of the first selection in a press release.[283]

On 17 December 2014, a team at Johns Hopkins developed a prototype breakaway hazmat suit. The project has been awarded a grant from the U.S. Agency for International Development (USAID) to develop. The prototype has a small, battery-powered cooling pack on the worker's belt, "You'll have air blowing out that is room temperature but it's 0% humidity ... the Ebola worker is going to feel cold and will be able to function inside the suit without having to change the suit so frequently," said one source.[284] In March, Google developed a tablet that can be cleaned with chlorine.[285] It is charged wirelessly and can transmit information to servers outside of the working area.[286]

Médecins Sans Frontières and American CDC staff preparing to enter an Ebola treatment unit in Liberia

Healthcare workers

In the hardest hit areas there have historically been only one or two doctors available to treat 100,000 people, and these doctors are heavily concentrated in urban areas.[211] Healthcare providers caring for people with Ebola and family and friends in close contact with people with Ebola are at the highest risk of getting infected because they may come in direct contact with the blood or body fluids of the sick person. In some places affected by the outbreak care may be provided in clinics with limited resources, and workers can be in these areas for several hours with a number of Ebola infected patients.[287] According to the WHO, the high proportion of infected medical staff can be explained by a lack of the number of medical staff needed to manage such a large outbreak, shortages of protective equipment or improperly using what is available, and "the compassion that causes medical staff to work in isolation wards far beyond the number of hours recommended as safe".[211] In August 2014, healthcare workers represented nearly 10 percent of the cases and fatalities—significantly impairing the ability to respond to an outbreak in an area already facing a severe shortage.[288] By 1 July 2015, the WHO reported a total of 874 health workers had been infected and 509 had died.[289]

Among the fatalities is Samuel Brisbane, a former advisor to the Liberian Ministry of Health and Social Welfare, described as "one of Liberia's most high-profile doctors".[290] In July 2014, leading Ebola doctor Sheik Umar Khan from Sierra Leone died in the outbreak.[70][291][292] In August, a well-known Nigerian physician, Ameyo Adadevoh, died.[293] Mbalu Fonnie, a licensed nurse midwife and nursing supervisor with over 30 years of experience at the Kenema hospital in Sierra Leone, died after contracting Ebola while caring for a fellow nurse who was pregnant and had Ebola. Fonnie was a co-author of a study that analyzed the genetics of the Ebola virus; five others contracted Ebola and died while working on the study as well.[294]

Basing their choice on "the person or persons who most affected the news and our lives, for good or ill, and embodied what was important about the year", in December 2014 the editors of Time magazine named the Ebola health workers as Person of the Year. Editor Nancy Gibbs said, "The rest of the world can sleep at night because a group of men and women are willing to stand and fight. For tireless acts of courage and mercy, for buying the world time to boost its defenses, for risking, for persisting, for sacrificing and saving, the Ebola fighters are Time's 2014 Person of the Year."[295]

Experimental treatments, vaccines and testing

Researcher working on the Ebola virus

There is as yet no known confirmed medication or treatment for Ebola virus disease. The director of the US National Institute of Allergy and Infectious Diseases has stated that the scientific community is still in the early stages of understanding how infection with the Ebola virus can be treated and prevented.[296][297][298] A number of experimental treatments are undergoing clinical trials.[299][300][301][302]

Ebola control is hindered by the fact that current diagnostic tests require specialised equipment and highly trained personnel. Since there are few suitable testing centres in West Africa, this delays diagnosis. As of February 2015 a number of diagnostic tests are under trial.[303] In September 2015, a new chip-based testing method that can detect Ebola accurately was reported. The new device allows for the use portable instruments that can provide immediate diagnosis.[304][305]

Several Ebola vaccine candidates had been developed in the decade prior to 2014, and had been shown to protect nonhuman primates against infection, but none had yet been approved for clinical use in humans.[306] Several trials are ongoing,[307][308] including an inhalation vaccine that has been shown effective in monkeys.[309]

On 31 July 2015, researchers announced that a vaccine trial in Guinea had been completed that appeared to give protection from the virus. The vaccine, formally called rVSV-ZEBOV but more commonly known as VSV-EBOV,[310] has shown 100% efficacy in individuals, but more conclusive evidence is needed on its capacity to protect populations through what is called herd immunity. To that end, the Guinean national regulatory authority and ethics review committee have approved continuation of the trial. The technique used in the vaccine trial is called ring vaccination, which was used in the 1970s to eradicate smallpox. Ring vaccination controls an outbreak by vaccinating all suspected infected individuals in the area around the outbreak.[32][33][54]


Since the beginning of the outbreak, considerable difficulty has existed in getting reliable estimates both of the number of people affected, and of the geographical extent of the outbreak.[311] The three most affected countries, Sierra Leone, Guinea and Liberia, are among the poorest in the world, with extremely low levels of literacy, few hospitals or doctors, poor physical infrastructure, and poorly functioning government institutions.[312]

Statistical measures

Calculating an accurate case fatality rate (CFR) is difficult for an ongoing epidemic due to differences in testing policies, the inclusion of probable and suspected cases, and the inclusion of new cases that have not run their course. In August 2014, the WHO made an initial CFR estimate of 53% though this included suspected cases.[313][314] In September and December 2014, WHO released revised and more accurate CFR figures, using data from patients with definitive clinical outcomes, of 70.8% and 71% respectively.[3][4][5] The CFR among hospitalized patients, based on three intense-transmission countries, is between 57% and 59%.[6]

The basic reproduction number R0 is a statistical measure of the average number of people expected to be infected by one person who has a disease. If the rate is less than 1, the infection dies out. If the rate is greater than 1, the infection continues to spread—with exponential growth of cases.[315] In September the estimated basic reproduction numbers were 1.71 (95% CI, 1.44 to 2.01) for Guinea, 1.83 (95% CI, 1.72 to 1.94) for Liberia, and 2.02 (95% CI, 1.79 to 2.26) for Sierra Leone.[3][316][317] On October 23, WHO noted that exponential increase of cases continued in the countries with the most intense transmission (Guinea, Liberia and Sierra Leone).[318]

Projections of future cases

On 28 August 2014, the WHO released its first estimate of the possible total cases (20,000) from the outbreak as part of its roadmap for stopping the transmission of the virus.[212] The WHO roadmap stated "this Roadmap assumes that in many areas of intense transmission the actual number of cases may be two- to fourfold higher than that currently reported. It acknowledges that the aggregate case load of Ebola could exceed 20,000 over the course of this emergency. The Roadmap assumes that a rapid escalation of the complementary strategies in intense transmission, resource-constrained areas will allow the comprehensive application of more standard containment strategies within three months."[212] The report included an assumption that some country or countries would pay the required cost of their plan, estimated at half a billion dollars.[212]

When the WHO released its first estimated projected number of cases, a number of epidemiologists presented data to show that the WHO's projection of a total of 20,000 cases was likely an underestimate.[319][320] On 9 September, Jonas Schmidt-Chanasit of the Bernhard Nocht Institute for Tropical Medicine in Germany, controversially announced that the containment fight in Sierra Leone and Liberia has already been "lost" and that the disease would "burn itself out".[321]

On 23 September 2014, the WHO revised their previous projection, stating that they expected the number of Ebola cases in West Africa to be in excess of 20,000 by 2 November 2014.[3] They further stated, that if the disease was not adequately contained it could become endemic in Guinea, Sierra Leone and Liberia, "spreading as routinely as malaria or the flu",[322] and according to an editorial in the New England Journal of Medicine, eventually to other parts of Africa and beyond.[323]

In a report released on 23 September 2014, the CDC analysed the impact of under-reporting which required correction of case numbers by a factor of up to 2.5. With this correction factor, approximately 21,000 total cases were estimated for the end of September 2014 in Liberia and Sierra Leone alone. The same report predicted that total cases, including unreported cases, could reach 1.4 million in Liberia and Sierra Leone by the end of January 2015 if no improvement in intervention or community behaviour occurred.[13] However, at a congressional hearing on 19 November, the director of the CDC said that the number of Ebola cases was no longer expected to exceed 1 million, moving away from the worst scenario that had been previously predicted.[324]

A study published in December 2014 found that transmission of the Ebola virus occurs principally within families, in hospitals and at funerals. The data, gathered during three weeks of contact tracing in August, showed that the third person in any transmission chain often knew both the first and second person. The authors estimated that between 17 percent and 70 percent of cases in West Africa were unreported – far fewer than had been estimated in prior projections. The study concluded that the epidemic would not be as difficult to control as feared if rapid, vigorous contact tracing and quarantines were employed.[325]

Economic effects

In addition to the loss of life, the outbreak is having a number of significant economic impacts. In March 2015, the United Nations Development Group reported that due to a decrease in trade, closing of borders, flight cancellations, and foreign investment and tourism activity fueled by stigma, the epidemic resulted in vast economic consequences in both the affected areas and even throughout African nations that experienced low or no cases of Ebola.[31] A September 2014 report in the Financial Times journal, suggested that the economic impact of the Ebola outbreak could kill more people than the disease itself.[326]

  • In August 2014 it was reported that many airlines had suspended flights to the area.[327] Markets and shops had closed due to travel restrictions, a cordon sanitaire, or fear of human contact, which leads to loss of income for producers and traders.[328]
  • Movement of people away from affected areas disturbed agricultural activities.[329][330] The UN [331] They warned that with all the quarantines and movement limitations placed on them, more than 1 million people could be food insecure by March 2015.[332] By 29 July, the World Bank had given 10,500 tons of maize and rice seed to the 3 hardest-hit countries to assist them to rebuild their agricultural systems.[333]
  • Tourism was directly impacted in affected countries.[334] In April 2014, Nigeria reported that 75% of hotel business had been lost due to fears of the outbreak;[335] the limited Ebola outbreak cost Nigeria 8 billion.[336][337] Countries in Africa that were not directly affected by the virus also reported adverse effects on tourism.[338][339][340] For example, in 2015, it was reported that Gambia's tourism had fallen below 50 percent,[341][342] Elmina Bay in Ghana had an 80% decrease in U.S. tourism,[343] and Kenya,[344] Zimbabwe,[345] Senegal, Zambia, and Tanzania also reported a drop in tourism.[346]
  • Some foreign mining companies withdrew all non-essential personnel, deferred new investment, and cut back operations.[330][347][348] In December it was reported that the iron ore mining company African Minerals had started the shutdown of its Sierra Leone operations because it was running low on income.[349] On 10 March, it was reported that Sierra Leone had begun to diversify away from mining, due to the country's recent problems.[350]

In January 2015, Oxfam, which works for disaster relief, indicated that a "Marshall Plan", a reference to the massive plan to rebuild Europe after World War II, was needed so that other countries can begin to financially assist those who have been worst hit by the virus.[351] The request was repeated in April 2015 when the West African countries affected the most by the epidemic asked for an $8 billion "Marshall Plan" to rebuild their economies. Speaking at the World Bank and International Monetary Fund, Liberian president Ellen Johnson Sirleaf said the large amount was needed for recovery because "Our health systems collapsed, investors left our countries, revenues declined and spending increased."[352]

The [356]

In October 2014, a World Bank report estimated overall economic impacts of between $3.8 billion and $32.6 billion, depending on the extent of the outbreak and speed of containment. The report expected that economic impact would be most severe in the three affected countries, with a wider impact across the broader West African region.[357][358] On 13 April 2015, the World Bank said that they would soon announce a major new effort to rebuild the economies of the three hardest-hit countries.[359] On 23 July, a World Bank poll warned "we are not ready for another Ebola outbreak".[360]

On 6 July 2015, Secretary-General Ban Ki-moon announced he would host an Ebola recovery conference to raise funds for reconstruction. The three countries hit hardest by Ebola need about $700 million to rebuild their health services in the next two years.[361] On 10 July, it was announced that the countries most affected by the Ebola epidemic will receive $3.4 billion to rebuild.[362][363] On 29 September, the leaders of both Sierra Leone and Liberia indicated at the U.N. the start of the "Post-Ebola Economic Stabilization and Recovery Plan".[364]


In July 2014, the WHO convened an emergency meeting with health ministers from eleven countries and announced collaboration on a strategy to co-ordinate technical support to combat the epidemic. In August they published a roadmap to guide and coordinate the international response to the outbreak, aiming to stop ongoing Ebola transmission worldwide within 6–9 months, and formally designated the outbreak as a Public Health Emergency of International Concern.[27] This is a legal designation used only twice before (for the 2009 H1N1 (swine flu) pandemic and the 2014 resurgence of polio) that invokes legal measures on disease prevention, surveillance, control, and response, by 194 signatory countries.[365][366]

In September, the United Nations Security Council declared the Ebola virus outbreak in West Africa "a threat to international peace and security" and unanimously adopted a resolution urging UN member states to provide more resources to fight the outbreak.[367][368]

During October, WHO and the UN Mission for Ebola Emergency Response announced a comprehensive 90-day plan to control and reverse the Ebola epidemic. The ultimate goal was to have capacity in place for the isolation of 100% of Ebola cases and the safe burial of 100% of casualties by 1 January 2015 (the 90-day target).[369] Many nations and charitable organizations cooperated to realise the plan.[370] A WHO situation report in mid-December indicated that the international community was on track to meet the 90-day target.[371] On 28 January 2015, the WHO reported that for the first time since the week ending 29 June 2014, there had been fewer than 100 new confirmed cases reported in a week in the three most-affected countries. The response to the epidemic then moved to a second phase, as the focus shifted from slowing transmission to ending the epidemic.[24] In May 2015, Dr. Margaret Chan indicated, "demands on WHO were more than ten times greater than ever experienced in the almost 70-year history of this Organization".[372][373] On 12 August, UNICEF indicated "hygiene protocols" have kept the virus out of all the classrooms.[374]

Criticism of WHO


There has been heavy criticism of the WHO from some aid agencies because its response was perceived as slow and insufficient, especially during the early stages of the outbreak.[28][375] In October 2014, the Associated Press reported that in an internal draft document the WHO admitted that "nearly everyone" involved in the Ebola response failed to notice factors that turned the outbreak into the biggest on record, and they had missed chances to stop the spread of Ebola due to "incompetent staff, bureaucracy and a lack of reliable information".[376] Peter Piot, co-discoverer of the Ebola virus, called the WHO regional office in Africa "really not competent."[377] In April 2015, the WHO admitted very serious failings in handling the crisis and indicated reforms for any future crisis; "we did not work effectively in coordination with other partners, there were shortcomings in risk communications and there was confusion of roles and responsibilities".[378] In May 2015, an independent panel indicated "deep and substantial" change would be needed by WHO;[379] on the same topic, the German chancellor Angela Merkel unveiled a strategy to improve WHO at the G7 meeting.[380][381]

Timeline of reported cases and deaths

Data sources

Data comes from reports by the World Health Organization Global Alert and Response Unit[Resource 1] and the WHO's Regional Office for Africa.[Resource 2] All numbers are correlated with United Nations Office for the Coordination of Humanitarian Affairs (OCHA), if available.[Resource 3] The reports are sourced from official information from the affected countries' health ministries. The WHO has stated the reported numbers "vastly underestimate the magnitude of the outbreak", estimating there may be 3 times as many cases as officially reported.[13][382][383]


Major Ebola virus outbreaks by country and by date – 7 June 2015 to most recent WHO / Gov update
Note: Cases include confirmed, probable and suspected per the WHO, numbers are the cumulative figures as published on the given date, and due to retrospective revisions differences between successive weekly totals are not necessarily the number of new cases that week.
Date Total Guinea Liberia Sierra Leone Sources
Cases Deaths Cases Deaths Cases Deaths Cases Deaths
25 Oct 2015 28,539 11,298 3,806 2,535 10,672 4,808 14,061 3,955 [note 2][384]
11 Oct 2015 28,454 11,297 3,800 2,534 10,672 4,808 13,982 3,955 [385]
27 Sept 2015 28,388 11,296 3,805 2,533 10,672 4,808 13,911 3,955 [386]
13 Sept 2015 28,220 11,291 3,792 2,530 10,672 4,808 13,756 3,953 [387]
30 Aug 2015 28,073 11,290 3,792 2,529 10,672 4,808 13,609 3,953 [388]
16 Aug 2015 27,952 11,284 3,786 2,524 10,672 4,808 13,494 3,952 [389]
26 July 2015 27,748 11,279 3,786 2,520 10,672 4,808 13,290 3,951 [390]
Minor Ebola virus outbreaks by country and by date – 30 July 2014 to most recent WHO / Gov update
Date Total Nigeria Senegal United States Spain Mali United Kingdom Italy Refs
Cases Deaths Cases Deaths Cases Deaths Cases Deaths Cases Deaths Cases Deaths Cases Deaths Cases Deaths
30 Aug 2015 36 15 20 8 1 0 4 1 1 0 8 6 1 0 1 0 [note 3][388]
29 Dec 2014 35 15 20 8 1 0 4 1 1 0 8 6 1 0 [note 4][5]
14 Dec 2014 32 15 20 8 1 0 4 1 1 0 6 6 [80]
2 Nov 2014 27 10 20 8 1 0 4 1 1 0 1 1 [391]
12 Oct 2014 23 8 20 8 1 0 1 0 1 0 - [392]
28 Sep 2014 22 8 20 8 1 0 1 0 - - [393]
30 Jul 2014 3 1 3 1 - [394]


  1. ^ The mortality rate (death/case ratio) recorded in Liberia up to 26th August 2014 was 70%.[4] However, the general estimated case fatality rate (70.8%) for this ongoing epidemic differs from the ratio of the number of deaths divided by that of cases due to the estimation method used. Current infections have not run their course, and the estimate may be poor if reporting is biased towards severe cases.
  2. ^ 25 Oct: All governments as per WHO.
  3. ^ No chance in Data from 13 May till 30 Aug
  4. ^ 29 December: All governments as per WHO. United Kingdom case dated 29 December.
  • Date is the "as of" date from the reference. A single source may report statistics for multiple "as of" dates.
  • Numbers with ≥ may not be consistent due to under reporting.


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External links


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