The entry of the H5N1 virus into eastern Europe has elevated concern over the bird flu virus, even though it hasn't developed the capacity to spread easily among humans.
Today, top U.S. health officials visited Vietnam, the country thought to be the most likely place for a global flu pandemic to arise from H5N1. During that visit, Health and Human Services Secretary Michael Leavitt told NPR that the Bush administration is working on a plan to ration Tamiflu, a scarce drug that's currently the only medical weapon against a pandemic flu virus. If a global outbreak occurred anytime soon, the nation's limited supplies of the drug would go first to medical personnel, said Leavitt.
The Emergence of Bird Flu in Humans
The H5NI strain of bird flu was first identified in 1997, when researchers traced an especially virulent flu infection in humans to exposure to bird flu in poultry markets. Eighteen people in Hong Kong were hospitalized, six of whom died.
At the time researchers thought the H5N1 strain marked the first time an influenza virus had jumped directly from birds to humans. New genetic work, however, suggests that the deadliest human flu virus ever, a 1918 pandemic that killed an estimated 50 million people, also started in birds.
The virus is easily spread among birds, but has not mutated into a form that makes it easily transmitted among humans. So far, humans have only been infected through direct contact with birds.
A look at recent outbreaks of bird flu among people, including several other significant new flu strains:
1999
Strain: H9N2
Caused illness in two children in Hong Kong, with poultry being the probable source.
2002
Strain: H7N2
Evidence of infection is found in one person in Virginia following a poultry outbreak.
2003
Strain: H5N1
Caused two Hong Kong family members to be hospitalized after a visit to China, killing one of them, a 33-year-old man. (A third family member died while in China of an undiagnosed respiratory illness.)
Strain: H7N7
Eighty-nine people in the Netherlands, most of whom were poultry workers, became ill with eye infections or flu-like symptoms. A veterinarian who visited one of the affected poultry farms died.
January 2004 through Oct. 10, 2005
Strain: H5N1
A total of 117 human cases of H5N1 were reported in Asia. Of these 60 (51%) were fatal. Human cases have been reported in Cambodia (4 cases, all fatal), Indonesia (5 cases, 3 fatal), Thailand (17 cases, 12 fatal), and Vietnam (91 cases, 41 fatal).
Strain: H7N3
Caused illness in two poultry workers in Canada.
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