Tamiflu resistance emerges

7 July 2009

The first report of pandemic H1N1 2009 virus resistance to oseltamivir (Tamiflu) came from Denmark last week followed by another report from Japan. There is now a third report from Hong Kong where the resistant virus was isolated from a patient who had not been treated with the drug. Resistance to Tamiflu has been well documented with seasonal flu and indeed in the last flu season in the USA more than 90% of cases showed resistance. As with all antibiotics and antivirals extensive use of  an agent will inevitably result in the emergence of resistant strains of the micro-organism. Given the widespread use of Tamiflu this development is not unexpected and it is also not unexpected that there should now be calls to restrict the use of the drug. It is reasonable to think that Tamiflu should be used only in vulnerable groups (pregnant women, those with underlying diseases, etc) especially as it appears that the pandemic virus disease is at least no more severe than seasonal flu. The alternative drug zanamivir (Relenza) is administered as an inhaled powder and therefore has not been as widely used as Tamiflu and resistance has not so far been reported.

Back to Alerts