Science in the News: The 2014 Ebola Outbreak

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Initial location of the Ebola outbreak highlighted in red, with the main road to the capital city Conakry also shown.

If you’ve been watching the news recently, you’ll probably have seen reports on the Ebola outbreak in West Africa. Around 673 people in Guinea and Liberia have died so far (including one case of a Liberian government employee who died shortly after arriving at Lagos airport in Nigeria), making this the most deadly outbreak to date. So what exactly is Ebola, and why is it so deadly?

Ebola virus disease (EVD) has an incredibly high mortality rate – while the current outbreak has a mortality rate of about 60%, EVD can be fatal in up to 90% of cases. It is caused by members of the genus Ebolavirus (part of the Filoviridae family), which includes five different species: Bundibugyo ebolavirus, Zaire ebolavirus, Reston ebolavirus, Sudan ebolavirus, and Taï Forest ebolavirus. The current outbreak was caused by Zaire ebolavirus. Fruit bats of the Pteropodidae family are the natural reservoir of the virus, and eating the bats can cause the virus to be transmitted to humans. In response to the outbreak, the Guinean government has banned the sale of bats for culinary purposes. Contact with infected chimpanzees (alive or dead) is another route of zoonotic transmission. Once a human becomes infected, they can transfer it to others via bodily fluids such as sweat, blood, and breast milk. Human-to-human transfer can occur from the febrile stage onwards, including after death – many people catch EVD while preparing bodies for funerals.

The initial symptoms include sudden fever, weakness, muscle pain, sore throat, and headache. Later, vomiting, diarrhoea, and kidney and liver problems develop. Perhaps the most ‘famous’ symptom is the haemorrhagic terminal phase, when patients bleed internally, vomit blood, and have reddened eyes. Not all patients develop these symptoms however – visible haemorrhage has occurred in less than half of the cases in the current outbreak. Haemorrhaging leads to kidney failure, breathing difficulties, shock, and eventually death. Death can occur as soon as one day after symptoms appear.

Without haemorrhagic symptoms, EVD can easily be confused with other diseases with similar initial symptoms, such as malaria, typhoid, meningitis, dengue fever, and Lassa fever. Therefore EVD needs to be diagnosed using laboratory tests; detection of Ebola RNA or antibodies in the blood, examination of samples using electron microscopy, and comparison of sample genomes with known Filovirus genomes are just some of the methods used to diagnose EVD.

Treatment for EVD involves treating the symptoms, as there is no treatment for the virus itself. Administration of fluid and electrolyte solutions to combat dehydration caused by diarrhoea, and medication to treat fever and gastrointestinal problems are the best methods of treatment currently available. There is some promising research into treating the virus itself; favipiravir, an antiviral drug, has produced promising results when used to treat laboratory-infected mice, and several vaccines are being developed and tested.

The severity and infectiousness of EVD means that controlling outbreaks is extremely important. Infected people must be quickly identified and quarantined, and people who have had contact with infected people must also be traced and monitored. Making sure bodies are transported and buried safely is also important, as several people infected in the current outbreak caught the virus while taking relatives’ bodies home and preparing them for funerals. Health care workers must make sure they practice good hygiene and wear protective clothing to avoid their patients transmitting EVD to them. Controlling outbreaks in rural Africa can be difficult however, as lack of education about transmission and treatment of EVD, and distrust of doctors and treatment methods means some people do not follow the advice of doctors and the World Health Organization. One example of this is the case of Sierra Leonean woman who was forcibly removed from hospital by her family and went on the run for several days before turning herself in.

With proper education and healthcare practices, EVD outbreaks can be contained and stopped. As more and more doctors from around the world arrive in West Africa to treat patients, hopefully this most recent outbreak will be over soon.

References:

http://www.who.int/mediacentre/factsheets/fs103/en/

Dixon MG, Schafer IJ, & EIS officer, CDC (2014). Ebola viral disease outbreak – west Africa, 2014. MMWR. Morbidity and mortality weekly report, 63 (25), 548-51 PMID: 24964881

Gatherer, D. (2014). The 2014 Ebola virus disease outbreak in West Africa Journal of General Virology, 95 (Pt_8), 1619-1624 DOI: 10.1099/vir.0.067199-0

Photo Credit:

http://www.nejm.org/doi/full/10.1056/NEJMoa1404505

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