Thursday, June 30, 2005

Not bad news is not necessarily good news

At least the latest news out of the WHO team visiting Vietnam isn't bad.
HANOI, June 29 (Xinhuanet) -- After spending one week in Vietnam studying bird flu, a WHO-coordinated international team of experts detected little change in the virus strain H5N1, concluding that there are no increased levels in the efficiency of transmission of the disease either from poultry to human or from human to human. (Xinhuanet)
But it's not quite clear exactly what the news is--or isn't. A team of international investigators went to Vietnam to see whether there was more infection with H5N1 than case counts indicated. Specifically there was question about whether investigation using Western blot of stored blood samples suggested this. Media reports, like the one from Xinhuanet above, are silent on this issue. Nor do we know on what basis the team made the judgment there are no increased (compared to what?) levels of transmission. It is not enough just assert this. Maybe the lack of information is a problem with the media, not WHO. But better and more detailed information is needed if pronouncements like this are to be accepted at face value.

The team also asked that future samples from suspect cases by shared with reference laboratories outside Vietnam "for external, independent confirmation as well as for quality assurance." We assume this will also give WHO access to sequence information to allow design of better primers for detection and confirmation as well as monitoring mutation. Not exactly a vote of confidence in Vietnam's ability to provide accurate information.

So the news wasn't bad. But just what it was, is less clear.

Update 6/30/05 (via Promed): excerpt of Statement from WHO
Some reports now circulating suggest that WHO has downgraded its assessment of the pandemic threat. These reports are unfounded. The experts were specifically asked to search for evidence that could substantiate concerns raised first at a WHO consultation of international experts held at the beginning of May in Manila. That consultation considered suggestive findings, largely based on epidemiological observations, that the H5N1 virus had changed its behaviour in ways consistent with an improved, though not yet efficient, ability to spread directly from one human to another. The specific epidemiological observations considered included milder disease across a broader age spectrum and a growing number of clusters of cases, closely related in time and place.

More recently, testing of clinical specimens by international experts working in Viet Nam provided further suggestive evidence of more widespread infection with the virus, raising the possibility of community-acquired infection. These findings have not been confirmed by the present investigative team.

Firm evidence of improved transmissibility would be grounds for moving to a higher level of pandemic alert. Because of the huge consequences of such a change, WHO is following a cautious approach that combines heightened vigilance for new cases with immediate international verification of any suggestive findings.

Because the detection of H5N1 in clinical specimens is technically challenging and prone to errors, members of the investigative team took sophisticated laboratory equipment with them to Hanoi for on-site testing. Tests were performed using WHO-approved reagents and primers.

While these first results are reassuring, further retesting of clinical specimens will continue over the next few weeks to provide the most reliable possible foundation for risk assessment.