Viral discovery efforts have an important role to play in controlling future epidemics. They contribute to a paradigm shift by incorporating a more proactive approach to surveillance and pandemic preparedness. Developing vaccines, improving public health infrastructure, and funding basic research are all critically important. But by also finding viruses in wildlife before they emerge in humans we stand to learn more about the ecology and evolution of viral diversity. We can also then test whether they pose a threat to humans. Our finding of a new ebolavirus in bats, Bombali virus, published in Nature Microbiology, is a good example of how we are trying to operationalize this paradigm.
As you can imagine, there is no silver bullet: Many of these viruses are rare and hard to find so it can come down to simple luck whether you find them or not. Did we happen to sample the right bat in the right place at the right time? People have been looking for ebolaviruses in bats for a long time, and so far this is the only full-genome that has been recovered from any bat. Of course, the virus people really want to find is Ebola virus (sometimes known as Zaire virus); that’s the one causing all the outbreaks – including the two recent outbreaks in the Democratic Republic of the Congo. Others in the field are still looking for that one, and we are too, so any clues we can get to help narrow the search are always helpful. Our study is useful in one way because it does increase our confidence that bats are where we would should be looking. But they also make it harder in another way. We have historically been focused on fruit bats and our finding now suggests that insectivorous might also be important.
The next step is to try and understand whether the Bombali virus is actually pathogenic. Most of the ebolaviruses that have been discovered can cause significant disease in people – but not all of them. Reston virus can infect people, but it doesn’t cause disease. The question now is whether Bombali is more like Ebola virus or Reston virus? It is entirely possible that the new virus is harmless, but given that the positive bats were found inside people’s houses this is an important question to answer. Of course, doing this is not straight forward either. We don’t have a virus yet, only the sequence, so we need to get an isolate or try and rescue the virus by reverse genetics. Until then we’re limited to in vitro studies of individual proteins to try and understand how they interact with human cells. And of course, we’re also actively engaging with the local communities in Sierra Leone that may be exposed to the virus, providing guidance on how to live safely with bats and planning for future surveys to see if the virus has spilled over into people.