“Diseases with a very high mortality, like Ebola, don’t usually persist because they are too effective at killing their hosts,” said Sherry Towers, a mathematical and computational modeling professor at Arizona State University. “A dead person can’t move around in the population and continue to spread disease to susceptible hosts.”
If a virus is slow to mutate — as Ebola appears to be — the pathogen gradually disappears from humans, for a couple of reasons. First, the percentage of the population that gets infected and develops immunity increases over time. Second, people modify their behavior and limit contact with one another. As a result, the virus finds it more difficult to spread and eventually runs out of human hosts.
At the end of past Ebola outbreaks, experts believe the virus retreated to its suspected animal reservoir, fruit bats. It may have lingered there for years until an infected bat came into contact with a human.
However, if the virus remains alive in at least some people, it remains an ongoing threat to public health.
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