¡¡  GENEVA, Aug. 18 (Xinhuanet) -- The World Health Organization (WHO)said Wednesday that two of the three fatal human cases of bird fluin Vietnam were identified as caused by strain of the H5N1 virus.

    The WHO said it is working with Vietnamese officials to furthertest whether the virus of the third case belongs to the same H5N1 strain that caused 22 cases, with 15 deaths, in Vietnam earlier this year.

    H5N1 is the only strain of the H5 subtype known to jump directly from infected poultry to cause illness in humans.

    Of the three cases confirmed as bird flu cases last week, two were in the north and one in the south of Vietnam. The most recent case died on Aug. 6 and no new cases have been identified since then.

    With support from Vietnam's Ministry of Health, arrangements are under way to send specimens from these cases to a laboratory of the WHO Global Influenza Surveillance Network, said the WHO.

    The laboratory will perform gene sequencing and other analyses of the virus in order to yield information immediately relevant toassessment of the public health risk.

    Studies will determine whether the virus responsible for these cases has mutated. It is particularly important to learn whether the H5N1 virus strain remains entirely of avian origin.

    The WHO said a small team of its staff will travel to Vietnam over the weekend. The team will be working closely with the Vietnamese authorities to assess the present risk to public health and to work out plans to strengthen surveillance capacity for the detection of human cases. Enditem