Frequently Asked Questions About Bird Flu
Has Bird Flu Been Seen in the U.S.?
H5N1 bird flu has never been detected in the U.S.
Various strains of bird flu pop up in U.S. poultry from time to time. When they do, all affected poultry flocks are culled.
For example, in 2004 a highly dangerous bird flu strain appeared in a Texas chicken flock. The outbreak involved an H5N2 virus (not the H5N1 bird flu). By April 2004, the outbreak had been eradicated. No human infections were detected.
While no human cases of bird flu have been seen in the U.S. or North America, the CDC is asking people who have traveled to East Asia to see a doctor if they develop flu-like symptoms. If so, it's important to tell the doctor about having visited these areas so the proper tests can be done.
What Are the Symptoms of Bird Flu in Humans?
Bird flu symptoms in people can vary. Symptoms may start out as normal flu-like symptoms. This can worsen to become a severe respiratory disease that can be fatal.
In February 2005, researchers in Vietnam reported human cases of bird flu in which the virus infected the brain and digestive tract of two children. Both died. These cases make it clear that bird flu in humans may not always look like typical cases of flu.
Bird Flu's Worst-Case Scenario
If a person -- or a susceptible animal -- gets infected with bird flu and human flu at the same time, the bird and human flu viruses could swap genes. Even without swapping genes, H5N1 could mutate into a form that more easily infects humans.
The lab-created H5N1 mutants remain in high-security labs. But the mutations needed to make H5N1 an airborne, human virus already exist in H5N1 viruses seen in nature. So far, the full set of mutations has not appeared in the same virus.
It would be bad news if H5N1 were to become as contagious as human flu. If it remained as lethal as it is now, the fatality rate would be about 58%. The deadliest flu bug in history, which caused the 1918 Great Pandemic, had a fatality rate of 2%.