Does the WHO Have the Info to Support Its Actions?

The World Health Organization has raised its pandemic alert level from 4 to 5 over the current swine flu outbreak:

Based on assessment of all available information, and following several expert consultations, I have decided to raise the current level of influenza pandemic alert from phase 4 to phase 5.

Influenza pandemics must be taken seriously precisely because of their capacity to spread rapidly to every country in the world.

On the positive side, the world is better prepared for an influenza pandemic than at any time in history.

Preparedness measures undertaken because of the threat from H5N1 avian influenza were an investment, and we are now benefitting from this investment.

For the first time in history, we can track the evolution of a pandemic in real-time.

I think that last sentence is key. Information and data are not necessarily synonymous.

The graphic above, from the WHO illustrates the phases referred to in the statement above.

In Phase 1 “no viruses circulating among animals have been reported to cause infections in humans.”

In Phase 2 a disease organism in the wild has spread from animals to humans and, consequently, has the potential to cause a “pandemic”, widespread disease among humans.

In Phase 3 there are outbreaks of the disease in several communities but insufficient human-to-human transmission to “sustain community-level outbreaks”. There may be limited human-to-human transmission.

In Phase 4 there are verified human-to-human transmissions of the disease sufficient to cause “community-level outbreaks”.

In Phase 5 there is “human-to-human spread of the virus into at least two countries in one WHO region. ” This is a caution to governments to take steps to deal with a major outbreak.

In Phase 6 there are “community level outbreaks in at least one other country in a different WHO region in addition to the criteria defined in Phase 5”. This is a global-level pandemic.

Is there an epidemiologist in the house? Is the WHO over-reacting? Specifically, does a disease need to pass through each phases in succession? Unless there are reports that I haven’t seen there doesn’t seem to be much human-to-human spreading of this disease outside of Mexico and even in Mexico the disease seems to be highly localized in the Mexico DF. Based on the published reports it seems to me that this disease is still in Phase 3.

I also wonder whether the distinction between Phase 4 and Phase 5 is still relevant. If there is essentially free travel between two countries is it a meaningful distinction? That’s certainly the case between Mexico and the United States.