How does pandemic influenza differ from common flu or avian flu?
Seasonal or common flu is a respiratory illness that can be transmitted person to person. Most people have some immunity, and a vaccine is available. Avian or bird flu is caused by influenza viruses that occur naturally among wild birds. On rare occasions, these bird viruses can infect other species, including pigs and humans. Some strains of avian flu, such as H5N1, are deadly to domestic fowl and can be transmitted from birds to humans. At this time the H5N1 virus cannot easily be transmitted from person to person. However, world health authorities are carefully monitoring the Avian H5N1 strain for its pandemic potential, since it could ultimately adapt into a strain that is contagious among humans. Once this adaptation occurs, H5N1 will no longer be considered a bird virus, but will be considered a human influenza virus.
