Viruses that normally occur in birds cause bird flu, and there are many different strains. Some of these viruses can pass from birds to other animals, and most of them are mild. However, there have been several human outbreaks of the H5N1 strain of bird flu in Asia and Europe over the last decade. Scientists are concerned that this strain will eventually mutate into a form that can pass directly from human to human. When the H5N1 strain re-emerged in Asia during the winter of 2003, it set off fears of a worldwide pandemic. (See How Bird Flu Works for more information.)
The flu vaccine that works against the A and B "regular flu" strains is not effective against bird flu. Although scientists are hard at work developing an avian flu vaccine, currently antiviral drugs are the only weapon against the disease.
Laboratory studies show that Tamiflu is effective against several strains of bird flu, including H5N1. It works the same way that it works against the "regular flu." However, it only lessens the severity of the illness -- it can't stop the virus entirely. The World Health Organization recommends Tamiflu as the drug of choice should an avian flu pandemic occur. Doctors in Asia are already using Tamiflu to treat patients who have become ill with the H5N1 strain.