WHO Epi Report

Bob Sims · medicine forum addict Joined: 24 Mar 2005 Posts: 98

Avian influenza - situation in Viet Nam - update 24

30 June 2005

At the request of the Ministry of Health, WHO sent a team of
international experts to Viet Nam last week to assess laboratory and
epidemiological data on recent cases and determine whether the present
level of pandemic alert should be increased. Team members were drawn
from institutes in Australia, Canada, Hong Kong SAR, Japan, the United
Kingdom, and the United States of America having extensive experience
in
the testing of avian influenza viruses in human clinical specimens.

The team completed its work on Wednesday and submitted its preliminary
findings to the government. The team found no laboratory evidence
suggesting that human infections are occurring with greater frequency
or
that the virus is spreading readily among humans. The current level of
pandemic alert, which has been in effect since January 2004, remains
unchanged.

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.

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