(March 3, 2009 - Insidermedicine) Flu viruses are rapidly developing resistance to the antiviral drug Tamiflu, according to research published in the Journal of the American Medical Association.

Here is some information about using antiviral drugs to treat the flu:

•    They can be used after you get the flu but do not replace vaccination.

•    They work by preventing the flu virus from reproducing in your system.

•    They can make your illness shorter and milder.

Researchers from the CDC analyzed data on flu virus samples submitted during the 2007-8 and 2008-9 flu seasons. They looked at what strains were most prevalent, whether they developed resistance to antiviral drugs, and what the characteristics of the people who had caught each strain were.

During the 2007-8 flu season, influenza A(H1N1) constituted nearly one-fifth of the circulating strains in the U.S. and 12% were resistant to Tamiflu. Data available so far for the 2008-9 season indicate that 98.5% of influenza A(H1N1) strains are resistant to Tamiflu.

We had a chance to speak with Dr. Nila Dharan, the principal investigator of this study, who offered some further insight.

Today’s research demonstrates a need to develop new antiviral drugs as well as better ways of preventing and treating the flu.

For Insidermedicine in Depth, I'm Dr. Susan Sharma.