• There are five identified Ebola virus strains, four of which are known to cause disease in humans.
• These are Ebola virus (Zaire ebolavirus); Sudan virus (Sudan ebolavirus); Taï Forest virus (Taï Forest ebolavirus, formerly Côte d'Ivoire ebolavirus); and Bundibugyo virus (Bundibugyo ebolavirus).
Uganda health authorities have declared an outbreak of Ebola disease. Ebola outbreaks emerge periodically in several African countries, most notably in the Democratic Republic of Congo (DRC). Public health expert Yap Boum, who has been involved in managing Ebola outbreaks in the past, answers some key questions about Ebola’s history, treatment, and how to keep safe.
What are the origins of the virus?
Ebola is an old and deadly disease that was discovered in 1976 near the Ebola river in northern DRC. The virus was named after the river. It was discovered by scientists including Jean-Jacques Muyembe – a Congolese microbiologist and general director of the DRC Institut National pour la Recherche Biomedicale – and researchers from the Institute of Tropical Medicine, including Stefaan Pattyn, Guido van der Groen and Peter Piot.
Professor Muyembe was called to the village of Yambuku in northern Zaire (now DRC) where a mysterious illness had broken out. He took a sample and sent it to the Institute of Tropical Medicine laboratory in Belgium, where the virus was isolated.
Since then, there have been five identified Ebola virus strains, four of which are known to cause disease in humans: Ebola virus (Zaire ebolavirus); Sudan virus (Sudan ebolavirus); Taï Forest virus (Taï Forest ebolavirus, formerly Côte d'Ivoire ebolavirus); and Bundibugyo virus (Bundibugyo ebolavirus).
It’s a zoonotic disease (animal-borne) though the natural reservoir host of Ebola virus remains unknown. However, bats are the most likely reservoir.
What are the symptoms of Ebola?
While the signs and symptoms may appear between 2 and 21 days after contact with the virus, they usually appear between 8 and 10 days.
They are quite similar to many tropical diseases, especially malaria and typhoid fever, with which they share symptoms such as:
- aches and pains, such as severe headache and muscle and joint pain
- weakness and fatigue
- sore throat
- loss of appetite
- abdominal pain
- diarrhoea and vomiting
- unexplained haemorrhaging, bleeding or bruising.
The main differences appear in the late stages of infection. These symptoms might include red eyes, skin rash and hiccups.
Can it be treated?
The Ebola virus disease can now be treated. The PALM clinical trial – implemented between 2018 and 2020 in the DRC – has evaluated four drug candidates. Two of them – Inmazeb and Ebanga – were approved by the US Food and Drug Administration in October and December 2020 to treat the Ebola virus disease caused by the Ebola virus. They are made available to patients by the World Health Organization (WHO) during Ebola outbreaks and aren’t available in the market.
Inmazeb is a combination of three monoclonal antibodies and Ebanga is a single monoclonal antibody. Monoclonal antibodies (often abbreviated as mAbs) are proteins produced in a lab or other manufacturing facility that act like natural antibodies to stop a germ such as a virus from replicating after it has infected a person.
Ebanga was isolated from a human survivor of the 1995 Ebola outbreak in Kikwit in the DRC who maintained circulating antibodies against the Ebola virus for more than a decade after infection.
Without treatment the average case fatality rate is approximately 50%. But it has ranged from 25% to 90% in past outbreaks.
Can it be prevented?
People can be vaccinated against one strain, the Zaire Ebola virus. It became a preventable disease following the validation of one vaccine candidate during the Ca Suffit Ebola clinical trial in 2015 in Guinea. The Ebola vaccine rVSV-ZEBOV (called Ervebo®) was approved by the US Food and Drug Administration in December 2019. This vaccine is given as a single dose vaccine and has been found to be safe and protective with a reported 100% efficacy.
Though it has not yet been approved by the US Food and Drug Administration, Johnson & Johnson has a two-dose vaccine for the Zaire strain that was used under emergency use in 2019 during an Ebola outbreak in the DRC. This vaccine requires an initial dose and a “booster” dose 56 days later and could be made available through the WHO during outbreaks.
How can you protect yourself?
Ebola is a highly transmissible disease but, aside from vaccination for the Zaire strain, its spread can be prevented through behavioural measures.
People should avoid contact with blood and body fluids – such as urine, faeces, saliva, sweat, vomit, breast milk, amniotic fluid, semen and vaginal fluids – of people who are sick. People should also avoid contact with their personal items which might have traces of these fluids.
People who were previously infected can still carry the disease in their semen.
Because it’s a zoonotic disease – that is, transmitted from animal to humans – people should avoid contact with bats, forest antelopes, nonhuman primates (such as monkeys and chimpanzees) and wild meat and blood especially in endemic areas.
Lastly, funeral or burial practices that involve touching the body of someone who may have died from Ebola should be avoided. Experience in West Africa shows these burial practices to be among the super spreaders of the Ebola virus.
Ebola virus disease is a deadly disease that is preventable and curable. The next step is the local production of diagnostics, vaccines and drugs to ensure that endemic countries control their own stock and can make them available to their population. Africa can’t be left behind once more when it comes to diagnostics, vaccines and treatment, as it has been during the COVID pandemic and monkeypox outbreaks.
Yap Boum, Professor in the faculty of Medicine, Mbarara University of Science and Technology
This article is republished from The Conversation under a Creative Commons license.