Concerted Effort Needed to Fight Drug-Resistant Flu Strain

By Amanda Gardner
HealthDay Reporter

TUESDAY, March 3 (HealthDay News) -- The global medical community needs to find new solutions to combat the growing resistance to a major flu-fighting drug, an infectious disease expert warns.

"The startling news about oseltamivir [Tamiflu] resistance should unite the global medical and scientific communities in an effort to cope with this rapidly evolving pathogen," wrote Dr. Anne Moscona, author of a perspective piece in the March 5 issue of the New England Journal of Medicine, and a professor of pediatrics and microbiology and immunology at Weill Medical College of Cornell University in New York City.

"For years, we have seen warning signals that highly oseltamivir-resistant influenza viruses could emerge and spread, disabling our defenses against this pathogen. Now the alarm has been sounded, and it is time to act," she added.

The good news is that there are other drugs that work against the flu strain showing resistance to Tamiflu, and your best protection is always the tried-and-true flu shot, experts say.

The resistance to Tamiflu to the H1N1 virus strain was not unexpected, according to Moscona, but the speed of the increase in resistance has been a surprise.

According to an article in this week's issue of the Journal of the American Medical Association, just 12 percent of virus strains last year were resistant to the antiviral drug. This year, that figure has soared to 98 percent. Last year was the first time resistance to Tamiflu was noted at all.

The resistance seems not to be in occurring in response to overuse of the drug, as so often happens with bacteria, but is, instead, "a natural, spontaneously arising variant," Moscona wrote.

Moscona, who has received financial support from pharmaceutical companies Medimmune, GlaxoSmithKline, Roche, Merck, NexBio and Shaklee, pointed to a number of drugs already available or in various phases of research that could be combined in a multi-drug campaign to combat flu resistance.

Some of the candidates are years away. But some, including Relenza (zanamivir), a cousin of Tamiflu, is already available, and another, peramivir, is in Phase 3 trials and close to being released, said Dr. Christine M. Hay, an assistant professor of infectious diseases at the University of Rochester Medical Center.

A multi-drug strategy is likely to be the most effective, Moscona stated, as resistance of virus strains to specific drugs becomes increasingly common.

Current drugs and others in the pipeline should be employed, Moscona wrote. These include:

• Giving Relenza intravenously. Relenza is a drug in the same class as Tamiflu, but has not yet seen resistance.
• Peramivir, an experimental neuraminidase inhibitor, is expected to be available intravenously as well as with a shot. Neuraminidase inhibitors are antiviral drugs that block a specific protein on the flu virus.
• Long-acting inhaled neuraminidase inhibitors, which are, again, not yet licensed, but could be used in one dose as a treatment or once a week for prevention of the flu. "It's not clear how useful this is going to be over what's already there," Hay said. "It's just going to act longer."

The encouraging news about the recent emergence of resistance to Tamiflu, the JAMA article noted, is that the resistant strain of flu is no more virulent than the "normal" strain.

H1N1 is the most common type of flu circulating in the United States. Also, the other two strains appear not resistant, and three other drugs available to fight the flu are still effective.

And as always, the best prevention against the flu is to be vaccinated, health officials emphasized.

"The first thing anybody should do always is to use the vaccine," said John M. Quarles, head and professor of microbial and molecular pathogenesis at Texas A&M Health Science Center College of Medicine. "That's the first line of defense."

More information

Visit the U.S. Centers for Disease Control and Prevention for more on the seasonal flu.