March 3, 2009
The flu bug might seem more severe this year, or it could be the drugs used to fight it just aren't working. That's the conclusion of a new Centers for Disease Control and Prevention (CDC) study, which concludes the most common flu strain has shown it can resist the main drug used to fight it.
"Influenza A (H1N1) viruses from 35 states have been tested for antiviral resistance to oseltamivir (Tamiflu) so far this season," the authors write. "To date, all influenza A (H3N2) viruses tested are resistant to the adamantanes and all oseltamivir-resistant influenza A (H1N1) viruses tested are sensitive to the adamantanes."
When they broke down the results, the researchers found that 98 percent of all H1N1 samples resist the effects of Tamiflu, a drug that is used to both prevent and treat flu viruses.
The CDC says influenza activity in the United States increased last week with influenza A (H1N1) the most common virus. The level of activity and the relative proportion of circulating virus types or subtypes have varied by region and may vary over the course of the season, the agency said.
"This presents challenges for the selection of antiviral medications for the treatment and chemoprophylaxis of influenza and highlights the importance of testing patients for influenza and consulting local surveillance data when evaluating patients with acute respiratory infections during the influenza season," the CDC said.
As flu seasons go, the 2008-09 season has been classified as relatively mild so far. The CDC says it has not classified outbreaks as "epidemics" in any region of the country this season. As many as 36,000 people in the U.S. die of flu each year.
