http://www.who.int/entity/wer/2005/wer8027.pdf
WHO: Avian influenza, Viet Nam
Avian influenza, Viet Nam
update1
During the penultimate week of June 2005, at
the request of the Ministry of Health, WHO
sent a team of international experts to Viet
Nam 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 Special Administrative Region of
China, Japan, United Kingdom and United
States having extensive experience in the
testing of avian influenza viruses in human
clinical specimens.
The team completed its work on 29 June 2005
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 consultation2 of international
experts held in Manila, Philippines,
on 6–7 May 2005. 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 epidemiolo-
gical 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 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 foundation possible for risk
assessment.
