Map of Ebola in the wild shows at-risk areas
Ebola is predicted to circulate in wild animals in twenty-two countries across West and Central Africa, making these countries at risk of future outbreaks.
Since the first outbreaks of Ebola virus disease in 1976, there have been numerous other outbreaks in humans across Africa with fatality rates ranging from 50% to 90%. Humans can become infected with the Ebola virus after direct contact with blood or bodily fluids from an infected person or animal. The virus also infects and kills other primates — such as chimpanzees or gorillas — though Old World fruit bats are suspected to be the most likely carriers of the virus in the wild.
The largest recorded outbreak of Ebola virus disease is ongoing in West Africa: more people have been infected in this current outbreak than in all previous outbreaks combined. The current outbreak is also the first to occur in West Africa — which is outside the previously known range of the Ebola virus.
David Pigott, Nick Golding and colleagues have now updated predictions about where in Africa wild animals may harbour the virus and where the transmission of the virus from these animals to humans is possible. As such, the map identifies the regions that are most at risk of a future Ebola outbreak. The data behind these new maps include the locations of all recorded primary cases of Ebola in human populations — the ‘index’ cases — many of which have been linked to animal sources. The data also include the locations of recorded cases of Ebola virus infections in wild bats and primates from the last forty years. The maps, which were modelled using more flexible methods than previous predictions, also include new information — collected using satellites — about environmental factors and new predictions of the range of wild fruit bats.
Pigott, Golding and colleagues report that the transmission of Ebola virus from animals to humans is possible in 22 countries across Central and West Africa — and that 22 million people live in the areas at risk. However, outbreaks in human populations are rare and the likelihood of a human getting the disease from an infected animal still remains very low. The updated map does not include data about how infections spread from one person to another, so the next challenge is to use existing data on human-to-human transmission to better understand the likely size and extent of current and future outbreaks. As more people live in, and travel to and from, the at-risk regions than ever before, Pigott, Golding and colleagues note that new outbreaks of Ebola virus disease are likely to be very different to those of the past.
To find out more
Listen to David Pigott discuss research on modelling the spread of ebola in episode 14 of the eLife podcast.
Read the eLife research paper on which this story is based: “Mapping the zoonotic niche of Ebola virus disease in Africa” (September 8, 2014).
Read a commentary on this research paper: “Epidemiology: Mapping Ebola in wild animals for better disease control”.
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