Thursday, May 19, 2005

WHO's chilling warning

CIDRAP has a superb rundown on the warning sounded at WHO's World Health Assembly in Geneva. Citing the "WHO Inter-country Consultation: Influenza A/H5N1 in Humans in Asia, Manila, May 6th-7th, 2005" (.pdf) CIDRAP sets out WHO's reasons for believing H5N1 is poised to become a pandemic threat:
The report cites several differences between epidemiologic features of human cases this year in northern Vietnam and those in southern Vietnam this year and overall last year:
  • Northern Vietnam has had eight case clusters this year, versus only two in the south.
  • Case clusters in northern Vietnam this year have lasted longer than did clusters last year.
  • The average age of infected people in northern Vietnam rose from 17 to about 31 years between 2004 and 2005, but it stayed about the same in southern Vietnam (15 to 18 years).
  • The case-fatality rate has dropped to 34% this year in the north but is 83% in the south.
In addition, the report says the recent discovery of three asymptomatic cases in Vietnam suggests that milder infections are occurring. A few asymptomatic cases also were found in Japan and Thailand in the past year, and others were discovered in Hong Kong after the H5N1 outbreak in 1997.

The report says the longer duration of recent clusters may signal a growing number of ways in which people contract the virus, including exposure to sick birds, environmental infection, lengthy exposure to asymptomatic birds that are shedding virus, and person-to-person transmission.


"Investigators were not able to prove that human-to-human transmission had occurred. However, they expressed concerns, which were shared by local clinicians, that the pattern of disease appeared to have changed in a manner consistent with this possibility," the assessment states.
A number of recommendations are made, including the following:
  • WHO should convene its Pandemic Task Force to meet regularly, assess the data, and determine the risk for pandemic flu.
  • All nations should move as quickly as possible to complete "practical operational pandemic preparedness plans."
  • WHO should explore "all possible mechanisms" to make H5N1 vaccine available to the Asian countries affected before a pandemic. It should bring together technical experts, countries, manufacturers and possible donors to find ways to boost global H5N1 vaccine production.
  • Coordination of animal and human surveillance and viral information must be improved from the ground level to the national and international level, and data must be exchanged quickly.
  • The WHO should complete a handbook on how to investigate possible H5N1 clusters.
  • The WHO should explore building a stockpile of antiviral drugs that could be used to respond to early signs of a potential pandemic.
  • Countries needing funding and agencies that may provide funding must coordinate their efforts to avoid redundancy and eliminate gaps
The WHO report concludes in chilling fashion:
"Evolution of a pandemic strain of virus may be preceded by numerous small steps, none of which is sufficient to signal clearly that a pandemic is about to start. This poses a difficult public health dilemma. If public health authorities move too soon, then unnecessary and costly actions may be taken. However, if action is delayed until there is unmistakable evidence that the virus has become sufficiently transmissible among people to allow a pandemic to develop, then it most likely will be too late to implement effective . . . responses."