The next Ebola?

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, though fruit bats are suspected to be the most likely carriers of the virus in the wild.

In the countries worst affected by the Ebola epidemic – Sierra Leone, Liberia and Guinea – hundreds of children have died in agony or been orphaned. The outbreak has also decimated already fragile healthcare systems killing doctors and nurses in countries with precious little of either.

Worryingly, a new report shows 28 countries are around the world are highly vulnerable to an Ebola-style epidemic because of weak health systems.

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. A new paper in eLife updates 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.

A growing body of scientific clues suggests that the Ebola virus may have lurked in the West African rain forest for years, perhaps decades, before igniting the deadly epidemic that swept the region in the past year, taking more than 10,000 lives. Until recently, Ebola had been considered a threat mostly to Central African nations. Yet studies tell of possible Ebola antibodies in human blood samples drawn in West Africa long before the current outbreak. And genetic analysis suggests the West African virus broke off from a parent strain in Central Africa at least 10 years ago, possibly as long as 150 years ago.

Medical detectives in West Africa are now seeking to establish whether the virus had previously infected people there. The research is part of a broader push to better understand where Ebola might strike next, and to strengthen surveillance and health systems in hopes of preventing future outbreaks.

Scientists estimate that between 1940 and 2004, 335 new infectious diseases appeared in humans. This number includes pathogens that likely entered our species for the first time, such as HIV, and newly evolved strains of familiar organisms, such as multidrug-resistant tuberculosis. The majority of these diseases—about 60 percent—were caused by zoonotic pathogens, meaning they were transmitted to humans from animals. And of those, about 70 percent were from animals that typically live in the wild. (Two of the last global pandemics—SARS and Ebola—were caused by viruses that appear to live in bats.) Interestingly, the percentage of human diseases coming from wild animals seems to be rising—and quickly. But why? And more importantly, what can we do about it?