Tamiflu misuse yielding drug-resistant strains of H1N1 virus

Indiscriminate use of antiviral medications making fight against swine flu much harder

August 31, 2009
Indiscriminate use of antiviral medications to prevent and treat influenza could ease the way for drug-resistant strains of the H1N1 virus, or swine flu, to emerge, public health officials warn -- making the fight against a pandemic that much harder.

Already, a handful of cases of Tamiflu-resistant H1N1 have been reported this summer, and there is no shortage of examples of misuse of the antiviral medications, experts say.

People often fail to complete a full course of the drug, according to a recent British report -- a scenario also likely to be occurring in the U.S. and one that encourages resistance.

Stockpiling is rife, and some U.S. summer camps gave Tamiflu prophylactically to healthy kids and staff. Experts anticipate more problems now as children return to school and flu season draws near.

"Influenza viruses mutate frequently, and any viral resistance could be acquired easily," said Dr. Anne Schuchat, director of the National Center on Immunization and Respiratory Disease at the Centers for Disease Control and Prevention in Atlanta. "It won't surprise us if we see resistance emerge as a bigger problem in the fall or in the years ahead."

Prescribed in pill form, Tamiflu works by preventing the flu virus from leaving infected cells and spreading to new ones. Because a vaccine against pandemic H1N1 influenza will not be widely available for several months, Tamiflu and to a lesser extent Relenza, an antiviral that acts similarly, are key medical tools for fighting the pandemic in the meantime.

This month, the World Health Organization advised doctors that even those sickened with the H1N1 virus do not need to be given Tamiflu or Relenza if they are mildly or moderately sick and are not in a high-risk group (such as children younger than 5, pregnant women and those with an underlying health condition).

Both drugs can help prevent illness in people exposed to the virus and reduce illness severity in people already sickened.

U.S. health authorities and those elsewhere are keeping a sharp eye on prescriptions of the drug as they prepare for a surge of H1N1 cases in the fall. The government has issued detailed guidelines on prescribing antivirals.

sroan@tribune.com