TORONTO - The World Health Organization signalled Tuesday it will not attempt to rewrite the definition of a pandemic to make disease severity part of the criteria for a pandemic declaration - something it hinted is coming soon because of swine flu.
But the Geneva-based agency said it will try to help countries mitigate anxiety over the declaration of a pandemic by devising a severity index and issuing advice on what countries should and shouldn't do in response to it.
The WHO's top flu expert said the idea is to help countries - some of which appear to feel locked into pandemic plans designed to respond to a far more severe pandemic - to "better calibrate their actions."
"One of the things that we hope to do by providing this kind of tailored guidance is really to help reduce some of the more drastic actions which may be uncalled for, but also to provide guidance to countries as to what steps they can take," Dr. Keiji Fukuda, WHO's acting assistant director general of health security and environment, said in a media teleconference.
"I think that some of the things that we would like to do is improve how we're able to communicate information, how we're able to provide guidance on what can be done in this situation so that actions that are really unnecessary and potentially anxiety provoking and unhelpful can really be modified or curtailed," he said.
Asked for examples of drastic or unhelpful actions, Fukuda pointed to the culling of pigs and shunning of pork products seen earlier in the swine flu outbreak.
The WHO's criteria for declaring a pandemic is based on the geographic spread of a new virus to which people have little or no immunity. The six-step pandemic alert scale says a pandemic will be declared when it is clear such a virus is spreading in the community in countries in two different WHO regions.
Currently the WHO says only North America has sustained community spread, though a number of countries appear to be on the cusp. Fukuda, who said a Phase 6 call is edging closer, mentioned Britain, Spain, Japan, Australia and Chile by name.
Confirmed community spread in any one of those, except Chile, would tip the balance for a pandemic call. (Though it is in the Southern Hemisphere, Chile is in the same WHO region as North America.)
However, recently a number of countries - some attending the meeting of the Association of Southeast Asian Nations, some attending the recent World Health Assembly in Geneva - urged the WHO to add severity to the criteria for a pandemic, suggesting the mild swine flu virus shouldn't make the cut.
On Monday, the WHO held a day-long series of consultations with more than 30 flu and public health experts from 23 countries around the globe.
In the end, Fukuda said, the consensus was that the current definition of Phase 6 should stand. But it was also agreed that a statement on severity should accompany the call, one that would hopefully help people understand that all pandemics aren't like the 1918 Spanish Flu.
He said the WHO will try to find a useful way to assess severity, suggesting a three-point scale is under consideration. The severity rating could change over time, he said, if the virus begins to behave differently or it takes a higher toll in different parts of the world.
An American influenza expert who was involved in the discussions said this is the right way to go to try to deter countries from taking actions that would cause more harm than good in the current circumstances.
Dr. Arnold Monto of the University of Michigan said pandemic planning was driven by concerns over the dangerous H5N1 avian flu virus. Consequently some countries have plans that may require them to take steps they don't need to take in response to this virus at this time.
"And that's the reason why a Phase 6 call has to be mitigated by a statement about the severity - even though it is difficult to do," Monto said from Ann Arbor.
"Even though most of us kept saying that H5N1 and a 1918-like pandemic is of questionable probability ... we really had little way of saying exactly what it was going to be," he said.
"We'd come up with predictions, but only on the basis of the knowns. And flu always surprises us in coming up with unknowns. Things that were unrecognized before."
The consultation also revealed that so far in the Southern Hemisphere - which is going into its winter - the virus is behaving as it has in the Northern Hemisphere. The disease patterns and unusual age distribution of cases appears to be the same, Fukuda said.
But there is early evidence which, if borne out, may support the experts' belief swine flu is a pandemic strain.
Fukuda said initial testing from Chile suggests the new virus has virtually crowded out the previous human strains of influenza.
"This has been one of the patterns that has been seen with the earlier pandemics. So I think that it bears very close watching," he said.
New strains have a biological advantage, because so many people are susceptible to them. In the 1957 pandemic, the new H2N2 virus became dominant, forcing the previous virus, an H1N1, back into nature. When H3N2 emerged in the 1968 pandemic, H2N2 disappeared.
This is one of several features about this virus that gives flu experts pause, Fukuda said, pointing also to sustained spread in the Northern Hemisphere in what is typically flu's off season and high attack rates and severe illness in a demographic group - young healthy adults - not typically at high risk from flu. These features too were seen in earlier pandemics.
"We have an unusual situation right here," he said.
