I'm a little late to the game on this topic, but it is something I want to speak on for a number of reasons. After quickly raising the H1N1 to the penultimate Pandemic Phase, the World Health Organization started to hesitate on following on to the final one. We are now, still, at Phase 5 of 6, defined as (
link to pdf) "The same virus has caused sustained community level outbreaks in two or more countries on one WHO region". I'm not going to second guess the rapid change
or the hesitation to push the button an call the outbreak a pandemic. That has been done by
others far
more ably than I could. Instead, I'm going to discuss the problem from my experiences as a local health department pandemic planner and now a Federal preparedness employee tangentially (to my job) involved in developing an internal pandemic response plan.
Is WHO redefining pandemic, as some have suggested? In my opinion, no. WHO is looking at altering its pandemic alert phases, and changing when it issues certain recommendations. A pandemic is an
epidemiologically defined event, and as such is not really something WHO can redefine. However, the
alert phases for a pandemic event are defined by WHO, and everyone else (see below) and as such, are open to redefinition. The current Phases were developed "
after three years of consultations and drafting, were drawn up while the WHO and the influenza experts who advise it were nervously watching the H5N1 avian flu virus". They weren't based on a pandemic-level outbreak and clearly were written (as were many of the existing plans) based on a single virus (H5N1). That being the case, I think a better question than "is WHO bowing to political pressure to redefine pandemic?" is "isn't it sound science to modify your hypothesis when you get more data?"
Should we include virulence, or some other measure, in the pandemic Phase? Dr. Racaniello argues that no,
virulence has no place is determining if an outbreak is pandemic, and he has far more epidemiology than I do. As he makes clear in his post "pandemic" is all about spread, not severity. I will argue, however, that in the definition of a
pandemic alert Phase, virulence is key. An outbreak with a low severity clearly requires a different response than one with a high severity, and the system that planners use to trigger actions needs to reflect this. You have the
WHO Phases, the
US Government Stages, DHS (yes, last time I checked they were
part of the US Government but that didn't stop them from developing their own) Pandemic Response Phases. In addition to these, the US government has also adopted a
Pandemic Severity Index. All of these together are enough to make planners pull out their hair.
I've been involved in drafting two plans. One, the Federal one, is tied to the USG Stages - we had multiple agency personnel involved in that planning effort and the USG Stages were the most apolitical set to go with. The H1N1 outbreak brought some problems with that plan to light, namely the fact that the USG Stage didn't change, but the area covered by the plan was in a part of the country that was significantly impacted. Had the outbreak been more virulent we would have been caught in a "steady state" mode. The other, a local health department (and foundation for the city) plan used the USG Stages, but more directly referenced a set of geographic triggers (clusters of cases at specific geographic distances from the city triggered a move to a higher level of activation). The H1N1 outbreak justified this approach, because it requires a certain concentration of cases at a specific distance away before activation. There were some cases, but not a sufficient quantity in any one location. The problem with this sort of approach for WHO is that it's awful tough to pick which location you're going to use as the center of your geographic triggers when you're making global recommendations.
Is WHO holding off declaring Phase 6 (Pandemic) for political/PR reasons? I've seen this discussed in a number of places, highlighting the resistance of certain UN member nations to calling the H1N1 outbreak a pandemic. I also think about the public health people, especially on the preparedness beat, that I've worked with. I think, less than political, there is concern at WHO that if they pull the pandemic card out now, for a currently low-severity outbreak they're going to have nothing left if it ramps up (as many fear it will) in the northern hemisphere come fall. The problem is that the system they have more or less requires them to call it a pandemic now, and that's why they're trying to rewrite on the fly.
I don't see an easy way out of this for WHO. They built a system of alerts based around a certain outbreak, if only subconsciously, and then got hit with a different one. I can see two ways forward. One is to simply follow the US model and add a severity index to the existing alert. That would allow them to call the H1N1 a pandemic, which it is, and then identify it with a severity of 1 or 2 and allow that to modify the response recommendations. The other is to try and develop a single system that includes both the geographic nature of the outbreak (the current system) and some factor of its virulence, which seems to be the way they are leaning. I fear that will only lead to confusion and further dissatisfaction given that they will continue to be seen as trying to dodge the "pandemic" label for H1N1, for whatever reason.
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