Flu Viruses Gaining Resistance, Study Confirms TUESDAY Dec. 7,
2010 -- Certain influenza virus strains are developing
increasing drug resistance and greater ability to spread, a new
study warns. American and Canadian researchers confirmed that
resistance to the two approved classes of antiviral drugs can
occur in several ways and said this dual resistance has been on
the rise over the past three years. The team analyzed 28
seasonal H1N1 influenza viruses that were present in five
countries from 2008 to 2010 and were resistant to both M2
blockers (adamantanes) and neuraminidase inhibitors (NAIs),
including oseltamivir and zanamivir. The researchers found that
additional antiviral resistance can rapidly develop in a
previously single-resistant influenza virus through mutation,
drug response, or gene exchange with another virus. The study
also found that the proportion of tested viruses with dual
resistance increased from 00.6 percent in 2007-08 to 1.5 percent
in 2008-09 and 28 percent in 2009-10. The findings a