The Ebola outbreak in West Africa was first reported in March 2014, and rapidly became the deadliest occurrence of the disease since its discovery in 1976.
In fact, the epidemic killed five times more than all other known Ebola outbreaks combined.
More than 21 months on from the first confirmed case recorded on 23 March 2014, 11,315 people have been reported as having died from the disease in six countries; Liberia, Guinea, Sierra Leone, Nigeria, the US and Mali. The total number of reported cases is about 28,637.
But on 13 January, 2016, the World Health Organisation declared the last of the countries affected, Liberia, to be Ebola-free.
Ebola deaths Figures up to 13 January 2016
- 11,315 Deaths – probable, confirmed and suspected (Includes one in the US and six in Mali)
- 4,809 Liberia
- 3,955 Sierra Leone
- 2,536 Guinea
- 8 Nigeria
The World Health Organization (WHO) admits the figures are underestimates, given the difficulty collecting the data. There needs to be 42 days without any new cases for a country to be declared Ebola-free. The outbreaks in Nigeria and Senegal were declared officially over by the WHO in October 2014. Sierra Leone and Guinea both had much larger outbreaks and it took a little longer. Sierra Leone was declared Ebola-free on 7 November 2015, Guinea followed in December.
Liberia has been the worst-hit, with more than 4,800 dead and 10,672 becoming infected. The WHO said that at the peak of transmission, during August and September 2014, Liberia was reporting between 300 and 400 new cases every week.
The epidemic seemed to abate and the outbreak in Liberia was declared over on 9 May 2015 – only to re-emerge seven weeks later when a 17-year-old man died from the disease and more cases were reported. The same happened in September, which is why the latest declaration of Liberia being Ebola-free, while welcome, should be treated with caution, say correspondents.
What is Ebola?
Ebola virus disease, or Ebola haemorrhagic fever as it was previously known, is caused by the Ebola virus. It is a rare but severe disease, found in countries in Africa, which can often have a fatal outcome (for 25-90% of the infected people). Transmission of the viruses occurs from person to person through direct contact with blood and other body fluids. The first documented outbreak of Ebola virus disease occurred in 1976 in the Democratic Republic of Congo, at the time known as Zaire, and all subsequent outbreaks have been in Africa.
What are the symptoms of Ebola?
In most cases, an infected person experiences sudden onset of fever, weakness, muscle and joint pains and headache, followed by progressive weakness, lack of appetite, diarrhoea (sometimes containing blood and mucus), nausea and vomiting. The initial symptoms are unspecific and are similar to other more common diseases such as the common cold or malaria.
The next stage is more severe with bleeding from the nose, gums and skin, and bloody vomiting and stools. Other symptoms include skin rash, inflamed throat and difficulty swallowing.
It can take between 2 and 21 days from the point of infection for a person to begin to show symptoms.
How can a person get infected?
A person can get infected with the Ebola virus by direct contact with infected blood, secretions, tissues, organs or other bodily fluids of dead or living infected persons. The risk for transmission in general is low in the initial stages of symptomatic patients. The virus can also be transmitted through material heavily contaminated with such fluids. It can also be contracted through unprotected sexual contact with patients who have recovered from the disease.
It is transmitted by droplets and not in the air, so it is highly unlikely that someone would be infected with Ebola virus disease just by coming into casual contact with someone already sick, such as sitting next to someone (and without any direct contact of bodily fluids).
Most people are infected from another person but some people have been infected with it from handling dead wild animals or ‘bush meat’ in Africa, such as chimpanzees and bats.
How contagious is it?
People only become infectious once they start to have symptoms. The risk of being infected in the early phase of symptomatic patients is generally low. The risk of infection is much higher in the later stages of the disease but can be effectively addressed with the proper use of appropriate personal protective equipment.
How deadly is it?
The case fatality rate – the proportion of people diagnosed with the disease who die – is 25-90% dependent on the virus type.
Is the virus resistant?
The Ebola virus is susceptible to disinfectants and bleach and is destroyed by heating.
Is there a vaccine?
There is no approved vaccine at this point but research is ongoing.
What is the treatment?
There is no specific treatment that is approved for general use against Ebola virus disease but supportive treatment – hospital care to relieve symptoms and to prevent further complications and side effects – can be given.
Where does it come from?
Ebola viruses are thought to circulate in wild animals in sub-Saharan Africa. They have been found in fruit bats, chimpanzees, gorillas and duikers, and human infections have been linked to direct contact with such animals.
How can an outbreak be stopped?
An outbreak of Ebola virus disease can be stopped by breaking the chain of transmission. This can be done by isolating suspected and confirmed patients to prevent onward transmission. At the same time, people who have been in close contact with patients are also contacted and monitored to identify possible infections.
If there is an Ebola outbreak in a country, does it mean that I shouldn’t travel there?
Check with your national authorities for travel advice on whether to travel to a country affected by an Ebola outbreak and other health information, including access to healthcare for reasons other than Ebola virus disease.
How can I protect myself against Ebola infection?
People visiting or residing in affected countries should take the following measures:
Avoiding contact with symptomatic patients and/or their bodily fluids
Avoiding contact with corpses and/or bodily fluids from deceased patients
Avoiding contact with wild animals (including monkeys, forest antelopes, rodents and bats), both alive and dead, and consumption of ‘bush meat’
Washing hands regularly, using soap or antiseptics
When to seek medical attention?
If you develop fever, muscle aches, weakness, headache and sore throat, you have been in a known affected area, having had contact with blood, secretions, organs or other bodily fluids of dead or living infected persons, you should seek rapid medical attention also mentioning your travel history
According to WHO on 18 March, two new cases of Ebola were confirmed in a rural village in the prefecture of Nzérékoré.
WHO declared the end of the recent flare-up of Ebola virus disease in Sierra Leone, 42 days after the last person confirmed to have Ebola virus disease in the country tested negative for the second time.
15 January 2016
Sierra Leone and WHO report a new confirmed case on 15 January 2016.
14 January 2016
Liberia was declared Ebola-free by the World Health Organization as forty-two days have passed since the second negative test of the last laboratory-confirmed case. All countries in West Africa involved in the epidemic have now been declared Ebola-free.
29 December 2015
Guinea was declared Ebola-free by the World Health Organization as forty-two days have passed since the second negative test of the last laboratory-confirmed case.
20 November 2015
The Liberian Ministry of Health and Social Welfare reported three confirmed cases of Ebola virus disease in Monrovia, Montserrado county.
7 November 2015
Sierra Leone was declared Ebola-free by the World Health Organization as forty-two days have passed since the second negative test of the last laboratory-confirmed case.
3 September 2015
WHO declares Liberia free of Ebola virus transmission in the human population as forty-two days have passed since the second negative test on 22 July 2015 of the last laboratory-confirmed case. Liberia enters a 90-day period of heightened surveillance.
2 July 2015
The sixth meeting of the Emergency Committee under the International Health Regulations (IHR) advised that the EVD outbreak still constitutes a Public Health Emergency of International Concern (PHEIC) and previously issued temporary recommendations should be extended.
2 July 2015
Ministry of health of Liberia reported a re-emergence localised EVD transmission in Margibi County resulting in three confirmed cases.
9 May 2015
WHO declares Liberia free of Ebola virus transmission
10 April 2015
WHO publishes a statement following the fifth meeting of the IHR Emergency Committee stating that the event continues to constitute a Public Health Emergency of International Concern (PHEIC).
10 March 2015
WHO declared the United Kingdom free of Ebola virus disease as 42 days have passed since the confirmed case tested negative.
23 January 2015
EVD vaccine developed by GSK ships to Liberia for phase-3 trial expected to start in February 2015.
21 January 2015
WHO publishes a statement following the fourth meeting of the IHR Emergency Committee stating that the event continues to constitute a Public Health Emergency of International Concern (PHEIC).
The USA is free of Ebola, 42 days from the date when the last patient tested negative.
17 November 2014
In Mali, WHO reported two additional cases in Bamako, all these cases are linked to an EVD imported case from Guinea on 25 October.
12 November 2014
In Mali, WHO reported three additional cases in Bamako that are not linked to the case reported on 23 October. Two are probable cases from Guinea, one was admitted in a clinic in Bamako on 25 October and died on 27 October, the second was a visitor of this patient who also died (the date of his death is not available). The two other cases are confirmed cases in HCWs who cared for the patient in the clinic. One died on 11 November.
1 November 2014
An UN worker was medically evacuated from Sierra Leone to France upon the request from WHO
28 October 2014
WHO published a press release regarding the approval of an Ebola vaccine trial at Lausanne University Hospital in Switzerland. The trial, which is being supported by WHO, is the latest in a series of trials that are ongoing in Mali, UK and the USA.
23 October 2014
The US Centers for Disease Control and Prevention (CDC) reported a new case in New York City. The case is a medical aid worker who volunteered in Guinea and recently returned to the United States. In addition, the Ministry of Health in Mali has reported that a two-year-old girl who recently arrived from Guinea has tested positive for Ebola. This is the first confirmed case of Ebola virus infection in Mali.
23 October WHO re-confirmed that the outbreak continued to constitute a Public Health Emergency of International Concern.
20 October 2014
WHO officially declared Nigeria free of Ebola virus transmission.
17 October 2014
Senegal was declared Ebola free
14 October 2014
In the USA, a second healthcare worker at Texas Health Presbyterian Hospital who also cared for the imported EVD patient tested positive for Ebola.
10 October 2014
In the USA, a healthcare worker at Texas Health Presbyterian Hospital who cared for the first imported EVD patient tested positive for Ebola.
6 October 2014
The Spanish authorities reported a confirmed case of EVD in a healthcare worker who cared for the second of two EVD patients that were evacuated to Spain.
3 October 2014
In Senegal, all contacts of the imported EVD case had completed the 21-day follow-up period without developing disease. No local transmission of EVD has been reported in Senegal. The imported case tested negative on 5 September and WHO declared Senegal free of Ebola on 17 October 2014 (two incubation periods after the last isolated case tested negative).
30 September 2014
The US Centres for Disease Control and Prevention (CDC) announced the first imported case of EVD in US linked to the current outbreak in West Africa.
23 September 2014
A study published by the WHO Ebola response team forecasted more than 20 000 cases (5740 in Guinea, 9890 in Liberia, and 5000 in Sierra Leone) by the beginning of November 2014. The same study estimated the doubling time of the epidemic at 15.7 days in Guinea, 23.6 days in Liberia, and 30.2 days in Sierra Leone.
18 September 2014
The United Nations Security Council recognised the EVD outbreak as a ‘threat to international peace and security’ and unanimously adopted a resolution on the establishment of an UN-wide initiative which focuses assets of all relevant UN agencies to tackle the crisis.
29 August 2014
The Ministry of Health in Senegal reported a confirmed imported case of EVD in a 21-year-old male native of Guinea.
8 August 2014
WHO declared the Ebola outbreak in West Africa a Public Health Event of International Concern (PHEIC).
End July 2014
A symptomatic case travelled by air to Lagos, Nigeria, where he infected a number of healthcare workers and airport contacts before his condition was recognised to be EVD.
Sierra Leone and Liberia reported the first cases. The disease is assumed to have spread from Guinea through the movement of infected people over land borders.
22 March 2014
The Ministry of Health in Guinea notified WHO about a rapidly evolving outbreak of Ebola viral disease (EVD). The first cases occurred in December 2013. The outbreak is caused by a clade of Zaïre ebolavirus that is related but distinct from the viruses that have been isolated from previous outbreaks in central Africa, and clearly distinct from the Taï Forest ebolavirus that was isolated in Côte d’Ivoire 1994–1995. The first cases were reported from south-eastern Guinea and the capital Conakry.
Ebola virus disease case definition
The classification of cases under this definition relies on clinical, epidemiological, laboratory and high-risk exposure criteria, allowing the identification of persons required to be investigated for EVD and the differentiation of probable and confirmed cases for reporting. The definition aims to classify cases for epidemiological reporting.
Any person currently presenting or having presented before death:
- Fever ≥ 38.6°C
AND any of the following:
- Severe headache
- Vomiting, diarrhoea, abdominal pain
- Unexplained haemorrhagic manifestations in various forms
- Multi-organ failure
OR a person who died suddenly and inexplicably
Any of the following:
- Detection of Ebola virus nucleic acid in a clinical specimen and confirmation by sequencing or a second assay on different genomic targets.
- Isolation of Ebola virus from a clinical specimen.
In the 21 days before the onset of symptoms:
- having been in an area with community transmission;
- having had contact with a probable or confirmed EVD case.
High-risk exposure criteria
Any of the following:
- close face-to-face contact (e.g. within one metre) without appropriate personal protective equipment (including eye protection) with a probable or confirmed case who was coughing, vomiting, bleeding, or who had diarrhoea; or had unprotected sexual contact with a case up to three months after recovery;
- direct contact with any material soiled by bodily fluids from a probable or confirmed case;
- percutaneous injury (e.g. with needle) or mucosal exposure to bodily fluids, tissues or laboratory specimens of a probable or confirmed case;
- participation in funeral rites with direct exposure to human remains in or from an affected area without appropriate personal protective equipment;
- direct contact with bats, rodents, primates, living or dead, in or from affected areas, or bushmeat.
On 9 October 2015, the UK notified an unusual late complication in an Ebola survivor. The case is a nurse who was diagnosed with EVD on 29 December 2014, after returning from Sierra Leone to Glasgow, via London. The nurse was treated with blood plasma from an Ebola survivor and an experimental drug closely related to ZMapp. She was declared free of Ebola on 24 January 2015. The nurse was transferred on 9 October from Queen Elizabeth University Hospital in Glasgow to the Royal Free Hospital in London, where she is treated – in accordance with national guidelines – in the hospital’s high-level isolation unit. As of 13 October 2015, the health authorities have identified 62 close contacts who will be closely monitored for 21 days. They will have their temperature taken twice daily, restrictions placed on travel and, in the case of healthcare workers, they were asked not to have direct patient contact during this period. Forty of the contacts had direct contact with the nurses’ bodily fluids and they have, as a precautionary measure, been offered vaccination with the rVSV-ZEBOV vaccine.
This is the same vaccine that has proved to be effective in the ongoing ring vaccination trial in Guinea. Twenty-six of the 40 have been vaccinated while 14 have either declined vaccination or had pre-existing medical contraindications. All 58 close contacts are being closely monitored for 21 days after their last exposure. The 26 who were vaccinated will undergo additional monitoring because the vaccine is still being evaluated.
ECDC threat assessment
Less than ten cases per week have been reported in Guinea and Sierra Leone since the end of July 2015, and transmission has remained confined to small areas in both countries.
No EVD cases have been reported worldwide during the last two weeks. This is the longest period without cases since March 2014. However, the risk of resurgence West Africa, and hence the risk of regional and global spread, will remain until all the most-affected countries have been declared Ebola-free. The Scottish health authorities are following up the nurse’s close contacts as a precaution. As of 13 October 2015, the health authorities have identified 62 close contacts, 40 of which had direct contact with the nurses’ bodily fluids . As a precautionary measure, close contacts having had direct contact with any type of bodily fluids were offered vaccination with rVSV-ZEBOV.
These vaccinations have now taken place. Twenty-six of the 40 accepted the vaccine. Fourteen have either declined the vaccine or were unable to receive it due to existing medical conditions. All 58 close contacts are being closely monitored for 21 days since their last exposure. They will have their temperature taken twice daily, restrictions placed on travel and, in the case of healthcare workers, they were asked not to have direct patient contact during this period. The 26 who were vaccinated will undergo additional monitoring because the vaccine is still being evaluated. In acute EVD, neurological symptoms of meningitis, encephalopathy, and seizures have been described.
In one case report, detectable viral load in CSF indicated that Ebola virus can cross the blood-brain barrier and thus have a pathogenic role in encephalitis. The authors concluded that treatment for Ebola virus disease should also target the central nervous system . However, there is as yet no evidence that the detection of Ebola virus in CSF during the acute illness is linked to relapse with CNS symptoms. Late manifestations of EVD, such as uveitis, were first described in 1999 . Information about late manifestations of EVD in association with RNA/viral reappearance in body fluids is limited. The continued detection of RNA and live virus in semen has been documented .
Further, persistence of the virus with long-lasting symptoms has been described once for Ebola virus. Viable virus was detected in aqueous liquid in the eye nine weeks after the clearance of viraemia and 14 weeks after disease onset in a patient presenting with uveitis. Long-term sequelae occurring over two years after Bundibugyo virus disease have been described, including neurological manifestations . The need for attention to the long-term sequelae in EVD survivors in the current West-African outbreak has been raised recently and some studies are ongoing . The risk of further transmission from the infected healthcare worker in the United Kingdom is considered very low, given the preventive measures taken and the continued monitoring of close contacts.
Contacts most at risk are those having cared for the patient prior to the adoption of protection measures and have potentially been exposed to bodily fluids. Further investigations are needed to fully understand the mechanism and impact of the re-appearance of viral RNA in this patient more than eight months after recovery. The patient received convalescent plasma when she was first treated for EVD eight months ago. It can only be speculated at this time whether treatment with convalescent plasma may influence an EVD patient’s immune response to the infection and the ability to clear the body of the virus. Ongoing cohort studies will hopefully provide more information about EVD survivors’ complications and longterm prognosis.