Chinese farmers, acting with the approval and encouragement of government officials, have tried to suppress major bird flu outbreaks among chickens with an antiviral drug meant for humans, animal health experts said. International researchers now conclude that this is why the drug will no longer protect people in case of a worldwide bird flu epidemic.
China's use of the drug amantadine, which violated international livestock guidelines, was widespread years before China acknowledged any infection of its poultry, according to pharmaceutical company executives and veterinarians.
Although China did not report an avian influenza outbreak until February 2004, executives at Chinese pharmaceutical companies and veterinarians said farmers were widely using the drug to control the virus in the late 1990s.
The Chinese Agriculture Ministry approved the production and sale of the drug for use in chickens, according to officials from the Chinese pharmaceutical industry and the government, although such use is barred in the United States and many other countries. Local government veterinary stations instructed Chinese farmers on how to use the drug and at times supplied it, animal health experts said.
[...] amantadine is not useful for treating H5N1 infections in Vietnam and Thailand, but it is effective against the vast majority of H5N1 isolates outside of Vietnam and Thailand (and probably Cambodia).
Third party reports on H5N1 outbreaks in western China have indicated that there have been human infections and media reports indicated the H5N1 isolated from bar headed geese in Qinghai Lake were similar to isolates in southeastern China. Thus, it remains to be see if this version of H5N1 has the amantadine resistant markers. Media reports on human cases in western China, suggest these isolates have the most dangerous combination of efficient human-to-human transmissibility and lethality.