What is bird flu and why is it a threat?
Like humans, birds can suffer from influenza but unlike the human illness, the bird disease is caused by avian flu viruses. Normally these viruses do not infect humans but some years ago a strain or subtype of avian flu virus called H5N1 was found to infect people, killing up to half of those infected. The virus does not possess the genetic traits that allow it to pass easily from one person to another, however the fear is that as more birds and people become infected, a mutation allowing person-to-person transmission is increasingly likely. If this occurred, then a global epidemic of a highly lethal form of human flu would belikely.
