Resistance to oseltamivir (Tamiflu) found in some European influenza virus samples

Preliminary results from a survey of antiviral drug susceptibility among seasonal influenza viruses circulating in Europe has revealed that some of the A (H1N1) viruses in circulation this winter are resistant to the antiviral drug, oseltamivir (also know by the brand name Tamiflu).  So far, 148 samples of influenza A(H1N1) viruses isolated during November and December from ten European countries have been tested by the EU funded VIRGIL network.  Of the 148 samples, 19 showed evidence of resistance to oseltamivir.

12 of the samples that tested positive for resistance to oseltamivir came from Norway.  This was from a total of 16 virus samples sent for testing.   Given the initial indication of a high level of resistance to oseltamivir in the A H1N1 viruses circulating in Norway, late last week once the information came to their attention, the Norwegian authorities notified their EU partners and the World Health Organization (WHO) of this situation.  The Norwegian Public Health Institute also published an advisory to doctors and the public on its website that evening.

Experts from the European Centre for Disease Prevention and Control (ECDC), the European Commission, and WHO are currently assessing the significance of the data from the VIRGIL network.  An interim joint assessment will be published in the coming days, based on the limited data currently available.

At this stage it is impossible to say what the level of resistance is in influenza across Europe. However from the limited data, the proportion of influenza viruses exhibiting resistance to oseltamivir must be significant, but not as high as in Norway.  People who become ill with the oseltamivir resistant strain of A(H1N1) do not appear to become any more sick than people infected with “normal” seasonal influenza.  That said, it should be remembered that any influenza A can cause severe disease or death in vulnerable people (older people, those with debilitating illnesses and the very young).  For information on seasonal influenza and how to protect yourself against it.

Read ECDC’s Interim Risk Assessment. ( 116 kB)