Ebolavirus disease (EVD) is a serious infectious disease that is often fatal in humans. This viral haemorrhagic fever of humans and other primates is caused by ebolaviruses transmitted to people from wild animals and spread through human-to-human infection.
It first appeared in 1976 in two simultaneous outbreaks, one in what is now Nzara, South Sudan and the other in Yambuku, Democratic Republic of the Congo. The latter occurred in a village near the Ebola River, hence the name. There have since been a number of outbreaks and six different types of ebola virus have been identified: Zaire, Bundibugyo, Sudan, Taï Forest, Reston and Bombali.
The 2014 to 2016 outbreak in West Africa started in December 2013, after an 18-month-old boy from a small village in Guinea is believed to have been infected by bats. The boy may have been infected by playing in a hollow tree housing a colony of fruit bats, say scientists. His death was followed by that of his older sister and then his mother. The virus soon spread to Guinea’s capital city and on March 13, 2014, the Ministry of Health in Guinea issued an alert for an unidentified illness. Shortly after, the Pasteur Institute in France confirmed the illness as Ebola. Ten days later, with 49 confirmed cases and 29 deaths, the World Health Organisation (WHO) officially declared an outbreak of Ebola virus disease. Two and a half years later, with widespread transmission to Guinea, Liberia, and Sierra Leone plus a handful of cases in Europe and the US, the outbreak ended with more than 28,600 cases and 11,325 deaths.
More recently, in September 2022, the Ministry of Health in Uganda confirmed an outbreak of Sudan ebolavirus disease in Mubende District after one fatal case was confirmed. On 11 January 2023, Uganda declared that this outbreak was over. Overall, nine Ugandan districts were affected (Bunyangabu, Jinja, Kagadi, Kampala, Kassanda, Kyegegwa, Masaka, Mubende, and Wakiso), 142 confirmed cases were reported of which 55 died (39 per cent) and 87 recovered. However, 22 deaths among probable cases were reported in people who died before samples could be taken (making the case fatality rate closer to 48 per cent). At least 19 healthcare workers were infected, of whom seven died.
How does Ebola spread?
The virus enters the body through cuts in the skin or when touching your eyes, nose or mouth – it’s worth noting that Ebola is not transmitted by air.
People get infected with Ebola from contact with infected animals. Ebola infections in people have been associated with hunting, butchering and eating wild animals which can lead to the transmission of zoonotic pathogens through animal bites, scratches, body fluids, tissues or faeces. There have been cases of people getting Ebola from fruit bats, monkeys, forest antelopes, porcupines and also chimpanzees and gorillas.
People also catch Ebola from other people who are infected through contact with body fluids such as saliva, urine, faeces, semen, blood or vomit. This is why healthcare workers have frequently been infected while treating patients with Ebola. People can spread Ebola as long as their blood contains the virus, even after they have died and, in the past, people have become infected at burial ceremonies that involved direct contact with the body of the deceased.
Early symptoms include fever, fatigue, muscle pain, headache and sore throat followed by more severe symptoms including vomiting, diarrhoea, rash and internal and external bleeding.
Pregnant women who get Ebola but recover may still carry the virus in breastmilk. See the WHO guidelines on the management of pregnancy and breastfeeding in Ebola.
The time from when you get infected to having symptoms can vary from two days up to three weeks. The chance of survival is about 50 per cent but in past outbreaks, up to 90 per cent of infected people have died.
If you recover from Ebola, you may still experience some symptoms, such as feeling tired, headaches, various aches and pains in all parts of the body, vision problems, weight gain, loss of appetite, hair loss and skin problems, insomnia, memory problems, hearing loss and even depression and anxiety.
Treatment
For people who get infected with Ebola, early supportive care is vital and includes rehydration to make up water losses (if the person cannot drink, they receive an intravenous drip), medicines for pain, nausea, vomiting and diarrhoea and also blood transfusions. Monoclonal antibodies can be used in adults and children against some types of Ebola but they are not widely available.
Some types of Ebola can be prevented with vaccines and treated with medicines. Other vaccines are currently in development.
Where did Ebola come from?
It’s thought that Ebola started infecting people because of bushmeat – the name for any wild animal that is killed for food including antelopes, chimpanzees, rats, porcupines, snakes and fruit bats. Fruit bats, of the Pteropodidae family, are natural Ebola virus hosts and are able to spread the virus without being affected by it. They can infect humans and other animals too.
The use of bats as food raises particular concern, as bats host more zoonotic viruses than most other animals. As we’ve seen, bats carry a whole range of viruses and in Africa’s Congo Basin, people eat an estimated five million tonnes of bushmeat per year, according to the Centre of International Forestry Research and Dr Olivier Restif, from the UK’s University of Cambridge, found that the scale of the bat bushmeat trade in Ghana was much higher than previously thought, with more than 100,000 bats killed and sold every year.
Exactly how virus spillover into humans occurs is not always clear, there is often an intermediary species involved, such as chimpanzees, but evidence shows people can get the virus directly from bats. Because the world’s population is expanding, close contact with wildlife will increase, which is often the first driver of emerging diseases. Deforestation is also a major contributor to recent outbreaks and cases of Ebola have often been close to recently deforested land.
The best way to prevent Ebola is to not kill and eat wild animals. Tennyson Williams, regional director for Africa for the animal welfare organisation World Animal Protection, says “The Ebola outbreak is an opportunity to clamp down on a practice which both causes disease outbreaks and empties forests of wildlife. At a minimum, governments should zealously enforce bans on the hunting and consumption of bats and apes, two groups most commonly associated with Ebola”.
“The time is right to end the smuggling and eating of wildlife” says Williams.