Network analysis of host–virus communities in bats and rodents reveals determinants of cross-species transmission

Luis, Angela D.; O'Shea, Thomas J.; Hayman, David T. S.; Wood, James L. N.; Cunningham, Andrew A.; Gilbert, Amy T.; Mills, James N.; Webb, Colleen T.

For cross-species transmission to take place, there must be contact, direct or indirect, between two host species, and therefore, it is not surprising that sympatry is important in the sharing of viruses. The importance of sympatry is reflected in similarities between viral and host species richness maps (Fig. 1 ). Locations where host species diversity is highest generally have more viruses. However, bats in Europe and India have greater viral richness than predicted by the host species richness map (Fig. 1a,c) , and this does not appear to be due to sampling bias (Fig. S7) . The community context may provide additional insight. There are two host-virus communities connecting Europe to East Asia where species richness is high (Fig. 3c,f) , and these communities may provide a bridge. Higher viral richness than expected from host species richness in India may also reflect connections with areas of high species richness in S.E. Asia (Fig. 3c) . For the viral richness maps, we assumed that the virus exists throughout the distribution of its host(s) analogous to the fundamental niche concept (Hutchinson 1957; Harris & Dunn 2010) and representing the broadest possible distribution. However, there may be barriers that restrict the realised niche of a virus. For example Rhinolophus ferrumequinum hosts SARS-like coronavirus and Japanese encephalitis virus, and its range extends from E. Asia to W. Europe, but the populations in E. Asia and Europe do not appear to mix (Flanders et al. 2009 ).