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CONFUSION surrounded reports last week that the H₅N₁ bird flu virus had been found in pigs in China.

Chen Hualan of China’s National Avian Influenza Reference Laboratory mentioned the findings at a flu symposium in Beijing on 20 August. Officials at the World Health Organization and the UN Food and Agriculture Organization were reportedly taken by surprise by her comments, and several news stories implied that Chen had let slip information China would rather have kept quiet.

In fact, although the full details have not yet been released, Chen’s team mentioned preliminary evidence of H₅N₁ infection in pigs in a prominent international journal more than a month ago. The discovery was reported in New ÐÓ°ÉÔ­´´ at the time (3 July, p 17).

If H₅N₁ is still infecting pigs in China – or in the other countries still struggling to contain outbreaks, such as Malaysia – it is not just bad news for pig farmers. The findings are worrying because it is thought that some past human flu pandemics began when pigs were simultaneously infected by bird and human viruses. The genes of two viruses may have intermingled to form a new, more lethal strain.