Several cases of the H1N1 ‘swine flu’ virus have emerged that are resistant to antiviral drug Tamiflu (oseltaminvir).
WHO has been informed by health authorities in Denmark, Japan and the Special Administrative Region of Hong Kong, China of the appearance of H1N1 viruses which are resistant to the antiviral based on laboratory testing.
However, the cases were shown to still be sensitive to Relenza (zanamivir) and WHO has confirmed that antiviral drugs remain a key component of its response to the pandemic.
The resistant viruses were found in three patients who did not have severe disease and who have all since recovered. Investigations have not found the resistant virus in the close contacts of these three people.
Close to 1000 pandemic H1N1 viruses have been evaluated by the laboratories in the Global Influenza Surveillance Network for antiviral drug resistance. All other viruses have been shown sensitive to both oseltamivir and zanamivir.
WHO and its partners have stated that they will continue to monitor influenza viruses for antiviral drug resistance.