How could the avian flu become transmissible between humans?
In order for the H5N1 virus to achieve human to human transmission, the virus itself will have to mutate. In the nine years that the virus has been monitored, it has shown that it can mutate relatively easily, being able to infect both domestic and wild birds, dogs, cats, (including tigers and leopards) and pigs. Of note, pigs are of concern because of the similarity of pig and human tissue. The H5N1 virus could potentially cross from birds to pigs, undergo a mutation, and infect humans more easily than going from birds to humans alone.
