Drug-resistant bird flu found in Vietnamese girl

WASHINGTON – A strain of H5N1 bird flu virus found in an infected Vietnamese girl is resistant to the drug being stockpiled by more than a dozen countries, including the United States, as a defense against a possible global pandemic, researchers reported Friday.

The new finding, while not unexpected, raises the possibility that oseltamivir, sold as Tamiflu, might be less useful than anticipated if resistant-strains of the H5N1 avian flu virus become more prevalent and the virus gains the ability to pass easily from person to person – a trait it does not possess now.

Friday’s report is the first indication that tests have detected a drug-resistant strain of H5N1 since the virus began circulating among birds in Asia. It was found in a 14-year-old Vietnamese girl who became ill in February while caring for her brother, who was also infected. She had initially received a low preventive dose of Tamiflu, and then a higher dose when she became ill. She recovered fully.

Tamiflu is in a class of antiviral drugs called neuraminidase inhibitors. Although resistant to Tamiflu, the strain reported Friday remained susceptible to another member of the class, zanamivir, sold as Relenza. All H5N1 viruses are resistant to the other main class of flu drugs, adamantanes, which include amantidine and rimantidine.

The H5N1 strain has infected 117 people in Southeast Asia and killed 60 since December 2003.