WHO confirms 5 Vietnam H5N1 cases, lists lab test criteria

Aug 31, 2007 (CIDRAP News) – The World Health Organization (WHO) today recognized five human H5N1 influenza cases from Vietnam dating back to late May, after publishing formal criteria for accepting positive test results for H5 flu viruses from national laboratories.

The five cases include four fatal ones, which pushes Vietnam's H5N1 toll to 100 cases with 46 deaths. The country has the second highest number of avian flu cases, after Indonesia.

The five cases now confirmed by the WHO had been reported earlier by Vietnamese authorities. The WHO apparently now has confirmed all the cases announced by Vietnamese authorities this year.

So far this year Vietnam has had seven H5N1 cases with four deaths, and the resurgence in human infections appears to have coincided with fresh poultry outbreaks, mainly in the northern and Mekong delta areas. Previously the country was widely hailed for keeping poultry infections at bay with strict control efforts, including an aggressive vaccination program, but many of the outbreaks this year have occurred in unvaccinated flocks.

In a statement yesterday about new criteria for accepting positive H5N1 findings, the WHO said it will now accept positive polymerase chain reaction (PCR) results from national reference laboratories that (1) have participated successfully in the WHO's new External Quality Assessment (EQA) project and (2) have accurately identified H5 flu viruses in at least three previous cases.

Tiffany Domingo, a technical officer in the WHO's outbreak and pandemic communications department, told CIDRAP News today that the WHO will now confirm positive H5N1 results from Vietnamese labs—as it did today for the latest five H5N1 case patients—so long as the labs meet the new testing criteria.

The WHO did not say which labs in Vietnam fulfilled the requirements, but in a Jun 29 statement on Vietnam's 93rd and 94th cases, the agency said the H5N1 infections were confirmed by the National Institute of Hygiene and Epidemiology (NIHE) in Hanoi, as well as the US Centers for Disease Control and Prevention (CDC).

Most countries that have had human H5N1 cases have had to send specimens to WHO reference labs elsewhere for testing and confirmation. However, the WHO has accepted positive H5N1 results from a few countries, such as China and, in recent months, Indonesia. In May the agency said it had formally assessed the Indonesian national laboratory's capacity to diagnose H5 viruses and would begin recognizing cases confirmed there.

Established in July, the EQA project is conducted by the WHO Global Influenza Programme at WHO headquarters in Geneva and the WHO reference laboratory at the National Influenza Centre in Hong Kong, according to a WHO statement issued in July. The program is designed to build the capacity of labs to use PCR to diagnose both seasonal and avian influenza and to support good laboratory practices. National influenza centers and laboratories are eligible to participate.

To participate in the EQA project, laboratories must test a simulated panel of RNA specimens twice a year and fill out a "Good Laboratory Practice" questionnaire. The RNA specimens include H1, H3, and H5 virus subtypes. The WHO analyzes the test results and reports on the performance of each laboratory.

In yesterday's statement, the WHO spelled out the two main requirements for accepting positive H5 test results from national laboratories:

  • The lab must participate in the EQA project and must have correctly detected all H5 viruses in the most recent set of samples, without reporting any false-positive H5 findings.
  • Since 2004, the lab must have tested for human H5 infections and must have made at least three positive diagnoses that were later confirmed by a WHO H5 reference lab.

Countries that don't have a national influenza reference lab, or have a national lab that has not met the WHO criteria, must have their positive H5 test results confirmed by a WHO reference lab or by another WHO-approved national reference lab.

See also:

Aug 31 WHO statement on Vietnam cases

July WHO statement on EQA project

WHO H5N1 avian flu case count

May 16 CIDRAP News story "WHO confirms backlog of 15 Indonesian H5N1 cases"

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