FAQ on the Ebola virus

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1. What are Ebola viruses and where do they occur?

In everyday language, people often talk about “the Ebola virus”, but this is just one virus within the Ebolavirus genus in the family of filoviruses. The Ebola virus refers only to what is often called Ebola-Zaire virus but there are other five viruses in the same genus, namely: Sudan virus, Bundibugyo virus, Reston virus, Tai forest virus and Bombali virus. Of these, Sudan, Bundibugyo and Tai Forest virus are capable of causing disease in humans, while Reston and Bombali are probably not pathogenic. 

Ebola, Bundibugyo and Sudan viruses cause severe hemorrhagic fever characterised by fever, headache, muscle pain, diarrhea, vomiting and, in severe cases, internal bleeding. Most outbreaks have been caused by Ebola virus (Ebola-Zaire), including the West African epidemic that caused more than 10,000 deaths. On average, across all outbreaks, the case fatality ratio for Ebola-Zaire is around 50 percent according to WHO. In recent years, survival has improved significantly because specialized treatment centers, antibody therapies and licensed vaccines against Ebola-Zaire are available. 

There is currently no licensed vaccine against disease caused by Sudan virus, but several vaccine candidates are in clinical testing. Bundibugyo virus is another filovirus that causes an Ebola-like disease. It also leads to severely ill patients and deaths. In the outbreaks documented so far, the case fatality ratio have averaged around 30 to 40 percent, lower than in many Ebola virus outbreaks but still high. For disease caused by Bundibugyo virus (BDBV), there is currently no licensed vaccine and no specific standard antiviral therapy. Treatment relies mainly on intensive supportive care. The current outbreak in the Democratic Republic of the Congo and Uganda is caused by Bundibugyo virus. 

However, the severity of EVD does not depend on the virus alone. Age, underlying conditions, nutritional status, timing of diagnosis and whether patients reach an experienced treatment center quickly are all crucial factors. Early diagnosis, isolation and high-quality intensive care can significantly improve survival.

Ebola outbreaks are regularly reported in countries in East and Central Africa, particularly in the Democratic Republic of Congo and Uganda. Major outbreaks have also occurred in West Africa, for example in Guinea, Sierra Leone and Liberia between 2014 and 2016.

2. What are the symptoms of infection?

After an incubation period of 2 to 21 days, the disease usually begins suddenly with high fever, severe malaise, headache and muscle pain. Vomiting, diarrhoea and abdominal pain often develop as the disease progresses.

Severe cases are accompanied by shock and multiple organ failure. Internal and external bleeding may occur. This is where the original name ‘viral haemorrhagic fever’ comes from, but these symptoms are rare. The mortality rate varies depending on the type of virus and medical care and ranges between 25 and 90 percent.

3. How is the Ebola virus transmitted to humans?

Certain species of fruit bats are believed to be the reservoir of the Ebola virus. Transmission to humans can occur when handling infected wild animals.

Human-to-human transmission occurs through direct contact with the bodily fluids of infected or deceased persons, as well as with contaminated surfaces or objects. Infection before the onset of the first symptoms is considered unlikely. Studies – including those involving the BNITM – also show that the Ebola virus can be detected in some bodily fluids for much longer than in blood. Semen has been particularly well studied, with virus components still being found months after the illness. Health authorities therefore recommend that men who have recovered refrain from sexual intercourse for a period of time or use condoms to prevent possible transmission.

4. What treatment is available?

There is no specific, widely applicable antiviral medication available. Treatment consists of supportive measures such as fluid and electrolyte replacement, stabilisation of the circulatory system and treatment of complications.

Approved vaccines are available for the Zaire ebolavirus. Vaccine candidates for other virus types are currently in clinical development.

5. How can you protect yourself from Ebola virus disease?

Consistent hygiene and protective measures are important: avoiding contact with potentially infected wild animals, wearing appropriate protective clothing in medical settings, and following safe procedures when handling contaminated materials.

In outbreak regions, there are clear guidelines for isolating sick people and safely burying the deceased. In addition, ring vaccinations are used, where available, to vaccinate contacts and contacts of contacts in order to interrupt chains of transmission at an early stage.

6. Further information

www.who.int/health-topics/ebola

www.ecdc.europa.eu/en/ebola-and-marburg-fevers

www.rki.de/Ebola.html