|OK they're cute, but are they deadly?|
I was lucky enough to appear alongside the guys over at This Week in Virology (thanks Vincent, Alan, Rich and Dickson) to discuss the recent publication of a paper (here in open access) which identified bats and rodents as potential animal reservoirs for a whole load of newly discovered RNA viruses, among other things. Check out the link above and enjoy what was an extremely fun and interesting hour and a half long experience.
The paper, from a large group of authors right across the world (actually when you look at where they looked, it wasn't all that much of the globe but I guess it is a sample after all), looked specifically for paramyxoviruses in bats and in rodents.
They picked paramyxoviruses because these viruses have been known to jump species from mammals into humans and other animals, they cause significant diseases (measles, mumps, respiratory infection and encephalitis and finally because I guess they had to focus somewhere. They actually tried unbiased 'deep sequencing' and quickly found it was heavily biased toward not finding paramyxoviruses. Possibly explaining the lack of paramyxovirus discovery in previous non-targeted efforts.
Their thinking was that these bats and rodents would have the potential to host a large number of viruses due to their high population sizes/densities, close contact with each other and potential to travel large distances (in the case of bats). Of course based on these criteria they could have looked in fish or birds but bats and rodents being mammals, there's a higher likelihood that their viruses could do really well in humans (although look at influenza and human metapneuomovirus). Although I bet you would find hundreds more if you explored the seas and the skies as opposed to the jungles.
They looked in over 10,000 individual animals from 15 places around the world, mostly in the tropics and were able identify 66 previously unknown 'species', more than doubling the potential number of potential paramyxoviruses previously known. They even identified the possibly first cousins of many of our deadly viruses, like mumps, nipah and respiratory syncytial virus.
They then took this further and looked at how viruses like these grew in bats, whether they caused disease and were the excreted and transmitted within and between bat populations. Instead of exploring what viruses were simply present, this group was more interested in establishing whether bats acted as an animal reservoir as knowing this would be excellent from a public health perspective. For example, what areas/species should be protecting and avoided from human contact.
Also from a purely biological perspective, if we assume that these closely related viruses (for example the 'bat mumps' virus) are well adapted to bats and not to humans and then vice versa for the human viruses, then the similarities and differences in functions of each component of the virus should be illuminating understanding how viruses jump species.