Public health concerns have been raised after two studies revealed that some influenza viruses are becoming increasingly resistant to antiviral treatments.
Influenza viruses are treated with two classes of drugs: M2 blockers (adamantanes) and neuraminidase inhibitors (NAIs), including oseltamivir and zanamivir.
But a new report from Dr Larisa Gubareva and colleagues at the Centers for Disease Control and Prevention and health agencies in West Virginia, Texas, USA, and Canada, has shown that dual resistance has been on the rise during the past three years.
Dr Gubareva analysed 28 seasonal H1N1 viruses with dual resistance from 2008 to 2010 from five countries.
Although dual resistant viruses are still rare, there was an increase in the number of tested viruses with this resistance, from 0.06 per cent in 2007-2008 to 1.5 per cent 2008-2009 to 28 per cent in 2009-2010. However, during the 2009-2010 season the number of circulating seasonal H1N1 viruses was low, and only 25 viruses were tested.
“Because only two classes of antiviral agents are approved, the detection of viruses with resistance to drugs in both classes is concerning,” said Dr Gubareva in the January 1 issue of The Journal of Infectious Diseases.
“If circulation of viruses with dual resistance becomes more widespread among any of the predominant circulating influenza A viruses, treatment options will be extremely limited.
“New antiviral agents and strategies for antiviral therapy are likely to be necessary in the future.”
A second UK-based study, also featured in the Journal of Infectious Diseases, examined an outbreak of oseltamivir resistant (OR) pandemic H1N1 infection in a haematology unit in the UK.
It is the first to confirm person-to-person transmission of this dually resistant strain through molecular epidemiologic methods.
“These findings suggest that oseltamivir may not be the frontline drug of choice in haematology patients, and zanamivir may prove to be more beneficial,” the study authors write.
The Journal of Infectious Diseases January 1 2010
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