The number of infections in humans from avian influenza continues to rise in Vietnam, and outbreaks among poultry have now been reported in virtually every province and city in the country.

By 9 February the death toll in Vietnam stood at 14 out of 19 confirmed cases. In Thailand the Ministry of Health reported five deaths and another 23 suspected cases, of which nine were fatal. Each case in humans presents another opportunity for the virus to combine with an existing human flu strain, reassort, and potentially spark a new flu pandemic.

The mortality in Vietnam of between 60% and 70% is much higher than the 30% mortality of the 1997 outbreak in Hong Kong, …