How does a virus travel from an animal like a pig to a human?
Viruses spread from one animal to another through close contact, in whatever manner it normally spreads, such as coughing or sneezing in the case of a respiratory virus. Normally, these infections have no impact on the new host since they were not built to infect them. But when one host is infected by two or more strains of a virus like influenza, new combinations can result. Influenza, for example, has eight distinct segments to its genome, increasing its ability to form new combinations that can include elements of avian flu, swine flu and human flu. It’s these recombined versions of the flu that have the potential to cross over and actually spread through a new host. Pigs are a particularly good incubator as they have receptors for influenza from all three species, said University of Guelph agriculture professor David Waltner-Toews, author of The Chickens Fight Back: Pandemic Panics and Deadly Diseases that Jump from Animals to People. “So, if they happen to be around people or bird
