Excessive use could aid deadly flu.

• Position: Antiviral Drugs

Influenza's ability to resist the effects of cheap and popular antiviral agents in Asia and Russia could give the U.S. pause concerning its plans to use Tamiflu in the event of widespread avian flu infection in humans, warn scientists at Ohio State University, Columbus.

Researchers analyzed almost 700 genome sequences of avian influenza strains to document where and when the virus developed resistance to a class of antiviral drugs called adamantanes and how far resistant strains spread. The analysis suggests that widespread antiviral drug use can accelerate the evolution of drug resistance in viruses, and that resistant strains can merge and spread rapidly.

The results should serve as a warning to those who consider Tamiflu the next great antiviral medication. Stockpiling Tamiflu has become a standard part of many government, business, and health organization plans to prepare for a long-feared pandemic flu outbreak, especially in the event that avian flu mutates enough to infect and be transmitted among humans easily.

"We can't necessarily say what we've seen in adamantanes is predictive of what will happen with Tamiflu but, in the larger dynamic, perhaps it serves as a cautionary tale," reflects Daniel Janies, associate professor of biomedical informatics. "Fighting infection is an arms race, and if we're not smart about how we use our arms and understand the evolutionary implications, then we will have ongoing and accelerating problems with drug-resistant microorganisms."

Resistance to adamantanes among strains of seasonal influenza spiked in...