Resistant Case of Swine Flu Found in S.F. Teen

Matthew B. Stannard, Chronicle Staff Writer
Wednesday, July 8, 2009

A San Francisco teenager has been diagnosed with a strain of swine flu that is resistant to the common antiviral drug Tamiflu - an important milestone in the pandemic's evolution.

The case suggests swine flu - a form of influenza Type A, subtype H1N1 - is capable of not only developing drug resistance but also spreading between humans in that resistant form, said Dr. Arthur Reingold, professor at UC Berkeley School of Public Health.

California Department of Public Health spokesman Ralph Montano said the teenager had developed some symptoms prior to a trip to Hong Kong but did not seek medical attention before boarding a plane.

"Hong Kong officials screened the teenager on June 11, upon arrival at the Hong Kong International Airport, and they detected a fever," he said. "The teenager was isolated in a Hong Kong hospital as a precaution and was discharged seven days later, which would be June 18."

The World Health Organization identified the teenager's virus as Tamiflu resistant Tuesday, one of three cases the organization has identified in the past two weeks.

It is not surprising that a Tamiflu-resistant form of the virus would develop, Reingold said: If a virus finds itself within a host that is taking an antiviral drug as a preventive measure, that virus may mutate to a form that can survive that drug.

The two other resistant cases - in patients in Japan and in Denmark - were taking Tamiflu prophylactically, said Dr Keiji Fukuda, assistant director-general of the WHO.

But the San Francisco teenager was not, which gives her case added significance, Reingold said, because it suggests she caught the resistant variant from somebody else.

The resistant strains remain treatable with another drug, generically known as Zanamivir, Fukuda said.