Dr. Andy

Reflections on medicine and biology among other things

Monday, November 28, 2005

Avian flu hype

This article, by Michael Fumento, effectively makes the case that an avian flu pandemic may never come and, if it does, it is unlikely to be as bad as we've been led to believe. While I overall liked the article, there are some things I disagree with. Fumento, although not a scientist or physician that I know of, obviously knows much more than most science writers about biology, virology, etc.

The one thing Fumento doesn't seem to appreciate is the power of evolution. He notes that H5N1 has been around for some time and doesn't yet effectively infect humans or spread from human to human. What he doens't discuss is that the more birds are infected the more virus there is replicating and the more chance of the emergence of a strain that is tropic for humans.

He also states
With all flu viruses, to paraphrase a bumpersticker, mutation happens. Avian flu could randomly mutate to be transmissible between humans. But it would indeed be random, since the virus is doing just fine in the bird population, thank you very much. There is no evolutionary pressure for it to reach out and infect other species. Such mutations nonetheless come along now and then. The infamous Spanish flu, for example, appears to have started as an avian flu.
This belies a fundamental misunderstanding of evolution. For any individual virus particle, it either infects another cell or it doesn't. Every avian flu viral particle in the world today is the progeny of a previous virus that managed to infect another cell. While the avian flu virus in aggregate is "doing just fine," imagine how many descendants the viral strain that infects a human and then spreads effectively to other humans will have. Of course evolution isn't anticipatory; that is, the virus can't somehow "know" what mutations are likely to be beneficial in the future. Mutations accumulate and then natural selection acts, not vice versa. So Fumento may be right that it is unlikely the requisite mutations for effective infection of humans will occur, but how well or poorly H5N1 is faring in birds isn't relevant (except that the more infected birds, the more virus replicating and the more mutations out there).

Also, despite the hype this article has generated, Fumento seems to agree we should keep working to mitigate the impacts of a pandemic, in case it does come.

1 Comments:

At 3:58 PM, Anonymous Colin Purrington said...

Nicely worded critique.

 

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