http://scienceblogs.com/effectmeasu...nd_lit.php#more

Swine flu: pictures, big and little
Category: Epidemiology • Infectious disease • Influenza treatment • Pandemic preparedness • Public health preparedness • Surveillance • Swine flu • Zoonoses
Posted on: April 29, 2009 1:05 PM, by revere

As is usual (routine? no, nothing routine about this) in an evolving epidemic contradictory and confusing numbers are appearing. Some of them are the result of information lags (tallies not being updated), some are the result of using different criteria for counting (suspect versus probable versus lab confirmed, etc.), some are just rumors. WHO is saying that in Mexico there are only 7 confirmed deaths, 19 more lab confirmed cases, 159 probable cases and some 1300 being evaluated, based on official reporting to them by officials of a member state, the Mexico. Everyone knows there are many more cases, however, so the WHO related reporting is more confusing than informative. CDC says there are 91 confirmed cases in the US on their swine flu page but 64 cases on the CDC home page as of 12:30 pm ET, 4/29). That's an information lag, within the same agency. The fact that there are more confirmed cases in the US than Mexico is not a reflection of how many cases are really in each place but how they are being recognized, confirmed, counted and updated.

It's not just lay people who are confused. The scientists don't seem to be on the same page all the time, either. The sequences have been published on the web and a scientist who has taken a hard look at them sees only swine sequences, not swine, bird and human as CDC announced originally:

With fast moving events it is quite understandable that early ideas would be revised, but when CDC's Dr. Anne Schuchat was asked point blank by a reporter at the Monday briefing if she could tell us which segments were human she gave a one word answer, "no." She then moved on to another question, so it wasn't clear whether she was refusing to answer or just didn't know. If CDC erred in this, as looks might be the case, the simplest thing would be to clear the record immediately and move on. This information isn't likely to make much difference in actions on the ground. An agency is much more credible when it acknowledges mistakes matter of factly (Obama is a master at this).

What's the take home message? We should stop fixating on hourly changes in numbers or differences about the sequences and keep our eye on the Big Picture. Right now that picture is still cloudy, but will be coming into sharper focus as new information accrues and is organized. Generally, though, we have a novel virus (in the sense that the human population is immunologically naive to it) that is spreading person to person and seems to have clinical characteristics not unlike usual seasonal influenza. Because of its novelty the number of people it could make sick is potentially far greater than a seasonal virus, however, since there is no naturally acquired immunity we know of at the moment (it may turn out there is some cross reactivity with some other strain from years past but so far we have no evidence of that).

As a Big Picture, it's not the most comforting, whatever the day to day numbers.

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