Tamiflu-resistant H1N1 in Denmark

ATLANTA – For the first time, a case of swine flu has proven resistant to Tamiflu — the leading pharmaceutical weapon against the new virus, international health officials said Monday.

The resistance was seen in a patient in Denmark, who has recovered.

"The goods news is they just found one," said Dr. Carolyn Bridges of the U.S. Centers for Disease control and Prevention.

It appears the strain developed in a patient who was taking the drug to prevent illness, and it has not spread to others. That's a much better scenario than if the patient had not been taking Tamiflu and picked up a drug-resistant strain already spreading through the public, said Bridges, associate director for science in the CDC's influenza division.

Also, it is not a mutation that includes pieces of both seasonal flu and the new pandemic form of the virus, according to Roche, the Switzerland-based pharmaceutical company that makes Tamiflu. Scientists have been worried about the new swine flu swapping genes with seasonal or other types of flu and perhaps mutating into a more dangerous or more infectious form.

Until an effective vaccine is developed, the drugs Tamiflu and Relenza have been considered the best available defense against the swine flu virus, which has caused nearly 28,000 reported illness in the United States, including more than 3,000 hospitalizations and 127 deaths.

Tamiflu resistance has not been seen in nearly 200 swine flu samples tested in the United States, Bridges said. But the resistance has been seen in other types of flu. Late last year, CDC officials reported that the most common flu bug circulating at the time was overwhelmingly resistant to Tamiflu. Health officials have believed it was probably a matter of time before a swine flu sample tested resistant, too.

The Danish case was isolated, however, and guidelines from the CDC and the World Health Organization continue to recommend Tamiflu as a treatment. No details were released on the patient's age or gender, or on when the patient was sick.

"It is possible to see occasional reports of resistance while a drug remains largely effective," said Terry Hurley, a Roche spokesman.