H1N1 cases defy Tamiflu

A cluster of four Tamiflu-resistant cases of H1N1 flu at Duke University Medical Center has raised concerns that changes in the virus may make severe infections more difficult to treat.

Three of the Duke patients died. All were adults, two women and one man, and they had other major diseases, said Dr. Cameron Wolfe, an infectious disease specialist at Duke. He said a fourth patient remains hospitalized.

Doctors use Tamiflu as the front-line defense to ease the symptoms and duration of flu infection, and international health authorities have been watching the H1N1 virus closely for signs it has mutated to overpower the therapy.

Another anti-viral drug, Relenza, remains potent, but it generally can't be taken by preschool-aged children or people with asthma and other respiratory diseases.

The Duke cluster comes at the same time a hospital in Wales reported five Tamiflu-resistant cases, and the World Health Organization began investigating a more virulent strain of H1N1 virus that appeared in Norway.

But state officials said Friday there is no evidence that a drug-resistant H1N1 strain is becoming dominant. In fact, they said, 99 percent of H1N1 flu cases remain treatable with Tamiflu.

"Reports of resistance have been very few," said Dr. Zack Moore, a medical epidemiologist with the state Division of Public Health. He said the Centers for Disease Control and Prevention has reported about 21 instances of resistant flu in the United States, not counting the Duke cluster or any others that might have come to light this week.

The Duke patients were housed in the same unit of the hospital over the past six weeks.

The CDC, which has headed the nation's response to pandemic flu, was called to investigate. Lab tests this week confirmed the patients all had the resistant strain. Wolfe said it remains unknown how and where the patients contracted the virus.

"We're trying to work back to see when their symptoms started to manifest, and when it looks like they may have come into contact with influenza," Wolfe said.

North Carolina has reported three prior instances of people coming down with Tamiflu-resistant flu, including the infection of two summer campers in the western part of the state that became a national case study.

Wolfe said it's highly unlikely the earlier cases and the current cluster are related.

However, worries over whether Tamiflu will remain an effective treatment against H1N1 are heightened by the flu virus' knack for evolving. Last year's strain of seasonal flu, for example, was widely resistant to the antiviral medicine.

Dr. Megan Davies, state epidemiologist, said the H1N1 virus continues to cause a relatively mild bout of illness, so most people who get sick have no need for Tamiflu.

"The mutation is a moot point to most of us," Davies said.

The development arises as cases of flu are beginning to taper off in North Carolina. After hitting a peak in mid-October, the state reported 489 new flu cases last week through its surveillance of participating doctors' offices, clinics and hospitals. But another spike in flu cases is expected as seasonal flu starts circulating later this winter.

Davies said the best protection against illness is a flu shot. She said the state has ordered 1.5 million doses of H1N1 vaccine so far this fall, and most have been delivered.

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