The team from the Geneva-based World Health Organization (WHO), which will travel to Viet Nam over the weekend, will work closely with the country’s Ministry of Health on plans to strengthen surveillance for detecting any further cases. Earlier this month WHO warned of the potential evolution of highly pathogenic avian influenza (H5N1) into a human pandemic after preliminary reports on the three new deaths, which followed an outbreak in South and East Asia earlier this year that infected 34 people, 23 of them fatally, and resulted in the deaths or culling of more than 100 million birds. Initial tests identified the latest virus as belonging to the H5 subtype and further testing has now confirmed that two of them are H5N1. WHO said it is particularly important to learn whether the H5N1 strain remains entirely of avian origin. The studies will determine whether it has mutated. The agency is concerned that continuing transmission of the virus to humans will give avian and human influenza viruses an opportunity to exchange genes, potentially giving rise to a new virus with pandemic potential. The most recent victim died on 6 August and no new cases have been identified since then. Arrangements are under way to send specimens from the new cases to a laboratory in the WHO Global Influenza Surveillance Network to perform gene sequencing and other analyses to yield information immediately relevant to assessment of the public health risk. Vietnamese health officials have called for close cooperation between WHO and the country’s two institutes equipped to test specimens for bird flu. This is expected to expedite the sharing of test results on any additional cases that might require investigation.