bird flu

Highly infectious form of the influenza virus that affects birds. The disease was thought to infect only birds until the first human cases were identified in Hong Kong in 1997. The symptoms of the disease in humans are similar to other types of flu, with characteristic sore throat, coughing, and high fever. However the death rate in those infected with the disease is significantly higher when compared with the fatality rates in the human forms of influenza. In the 1997 outbreak one-third of the 18 people infected with the disease died. In the outbreak in December 2003-early 2004, 20 people died.

Humans can become infected only if in close proximity to live infected birds by the inhalation of their excrement that has dried and been reduced to powder. There are 15 known strains of the bird flu virus, of which the H5N1 strain has been found to be transferable to humans. The scale of the bird flu outbreaks has been very small compared with recent health emergencies such as SARS; in the SARS outbreak 800 people died, compared to 26 deaths in both bird flu outbreaks combined. However, scientists consider the real danger with bird flu to be the possibility that the avian virus could exchange genes with the human form of the virus if a person happened to be infected with both forms of the disease simultaneously. This could result in a highly infectious new form of the human virus that would have the same high mortality rate as the bird form of the disease.

Researchers are working on the development of a vaccine. There have been no confirmed cases of a human passing this form of the disease on to another human.