Flu viruses are becoming increasingly resistant to antiviral drugs, according to a Dutch study reported in the journal Antiviral Research.
Says Dr Marcel Jonges: “Effective treatment or prophylaxis of influenza is becoming more and more complicated because hospitals and nursing homes cannot base appropriate antiviral therapy on national influenza surveillance drug susceptibility data.”
This follows an analysis by the National Institute for Public Health and the Environment in Bilthoven of the antiviral profiles of 273 cases between 2005 and 2008.
They report that adamantane-resistant A(H3N2) viruses increased from 74% in 2005-2007 to 100% in 2007-2008. All isolated A(H1N1) viruses were sensitive, and the presence or absence of S31N mutations in M2 protein was the major determinant.
Prior to 2007-2008, 98% of types A and B influenza viruses were sensitive to both oseltamivir and zanamivir. In 2007-2008, however, 24% of the A(H1N1) viruses were oseltamivir-resistant. They remained sensitive to zanamivir and the adamantanes, however.
The oseltamivir-resistant A(H1N1) or adamantane-resistant A(H3N2) viruses and the sensitive variants produced similar clinical symptoms, the report indicates.
Says Dr Jonges: “Fast and reliable point-of-care antiviral resistance tests are needed to start treatment with the functional antiviral drug, and monitor the emergence of resistance during treatment.”
Copyright Press Association 2009