More Evidence That H5N1 Influenza Could Trigger a Pandemic

Infection of humans with H5N1 influenza (“bird flu”) virus has been fatal about 60% of the time. The virus remains widespread among birds but has not developed the capacity to spread easily from human to human. Some experts think the virus simply cannot mutate into a form that spreads easily among humans, but others call that hypothesis wishful thinking.

New flu viruses develop from the recombination of genes from different flu viruses that live in the same animal. Both the H5N1 “bird flu” virus and the 2009/H1N1 “swine flu” virus that triggered a pandemic in 2009 can infect pigs. Experiments reported last year demonstrated that viruses containing mixtures of particular H5N1 genes and H1N1 genes can spread easily among ferrets, a mammalian m…