How Ebola Adapted to Us

Nov 4, 2016

By Ed Yong

In December 2013, in a small village in Guinea, the Ebola virus left its traditional host—probably a bat—and infected a young boy. That leap triggered what became the largest Ebola outbreak in history. At first, the virus stayed within Guinea’s borders and, as in every previous epidemic, affected just a few hundred people. But in the spring of 2014, that gentle simmer came to a disastrous boil. Cases skyrocketed as the virus spread to Sierra Leone, Liberia, and other countries. By the time it was finally brought to heel in 2016, more than 28,000 people had been infected and 11,000 of them were dead.

The unprecedented scale of the outbreak gave the virus ample opportunities to adapt to its new human hosts—and it took advantage of them. Two independent teams of scientists have shown that in early 2014, Ebola virus picked up a mutation called A82V, which made it worse at infecting bat cells, but better at infecting human ones. And once viruses with that mutation appeared, they quickly took over. They were the ones that spread beyond Guinea, the ones responsible for the vast majority of cases, the ones that landed in a Texan emergency room.

Both groups emphasize that the mutation may not have caused the virus’s exponential spread. “Its appearance coincided with the virus taking off, but others factors were probably more important, like the movement of infected people into urban areas and lack of proper burials,” says Jonathan Ball from the University of Nottingham, who led one of the teams. “If we hadn’t seen that mutation, there would probably still have been a big outbreak.”

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2 comments on “How Ebola Adapted to Us

  • Ebola could borrow a trick from HIV. If it killed the host more slowly, there would be more time to find new victims. I would think the evolutionary pressure would be in that direction. That it kills so quickly is an indication of how recently it hopped to human hosts.

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  • Roedy, I agree with you 100%. But if Ebola ever does reach that level of success, with a longer incubation period and less deadly results, I fear it would not be looked upon with the same level of urgency that it is now.

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