In the beginning, all flu viruses came from birds. Over time, the virus evolved to adapt to other animals, including humans, as natural selection favored viruses with mutations that allowed them to more readily infect the cells of new host species.
Fuente : http://www.eurekalert.org/pub_releases/2013-10/uow...
Fuente : http://www.eurekalert.org/pub_releases/2013-10/uow...