Medical Health Encyclopedia

Based on a final analysis of the 2001-2002 flu season, nearly 90% were type A and about 10% were type B. Influenza A usually causes more severe disease than type B. There is some concern, however, that since influenza B has been less common in the past few years, some people, particularly small children, may have fewer antibodies to it and so may be at higher risk for severe infection.

Avian Influenza (Bird Flu)

Although the risk of lethal viruses is generally low, scientists are greatly concerned about a particular virus called H5N1, which causes avian influenza (bird flu). Since 1997, the H5N1 virus has triggered deadly outbreaks in poultry across Southeast Asia. As of February 6, 2006, at least 165 people had been infected with the bird flu in 6 countries. More than half of these people have died, according to the World Health Organization. No cases have been seen in the United States.

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So far, the virus has spread from birds to humans.  The virus does not seem to be easily spread from person to person. However, scientists and public health officials are monitoring the spread of H5N1 and working to contain it. Efforts include slaughtering infected birds, developing new vaccines, and stockpiling antiviral drugs such as oseltamivir (Tamiflu). Many poor nations have limited resources and already contend with other serious health problems, including HIV-AIDS. If H5N1 does mutate and spread, the consequences could be especially severe for these countries.