How viruses skip from host to host has been revealed in a new study.
HIV-AIDS. SARS. Ebola. Bird Flu. Swine Flu. Rabies-these are emerging infectious diseases where the viruses have jumped from one animal species into another and now infect humans.
This is a phenomenon known as cross-species transmission (CST) and scientists are working to determine what drives it.
Researchers have claimed that that cross-species transmission may have less to do with virus mutation and contact rates and more to do with host similarity.
Led by Gary McCracken, a professor at the University of Tennessee, Knoxville, the team made their discovery by analysing hundreds of rabies viruses in 23 species of bats.
The researchers documented over 200 examples of CSTs and analysed the best explanations for CSTs, such as geographic range, behaviour, ecology and genetic relatedness.
The study found that the majority of viruses from cross-species infections were tightly nested among genetically similar bat species.
"It turns out, the most important factor in cross-species transmission is how closely related the bat species are," said McCracken
"Our study demonstrates that rapid evolution can be insufficient to overcome phylogenetic barriers at two crucial stages of viral emergence: initial infection and sustained transmission," he added.
His article, 'Host Phylogeny Constrains Cross-Species Emergence and Establishments of Rabies Virus in Bats', appears in the latest edition of Science and will be featured on the issue's cover.