Map of life expectancy at birth from Global Education Project.

Wednesday, June 29, 2005

Influenza Primer

Some of you may have clicked over to Effect Measure and discovered that Revere is, well, just a tiny bit worried about a killer flu pandemic. It occurs to me that the average person probably doesn't have all the basic info about this, and certainly isn't getting it from CNN, so I thought I'd give y'all the 411.

There are three major sub-types of influenza virus. B and C don't cause big problems but type A is a major drag on the human condition -- in part because it's also a bummer for pigs, horses, Flipper and Shamu, and birds, which means we can't get rid of it. Influenza A replicates sloppily, which means it is constantly mutating. These small mutations are why the flu shot you got last year won't work this year. But the even worse part is that the virus can swap whole gene segments.

That's bad because the virus has a protein called haemaglutinin (HA) that sticks out from its surface and gets it into cells. There are 15 known major sub-types of HA, in virus that infects birds, but only 3 sub-types are known to have been prevalent in the human population -- called H1, H2, and H3. So, if a variety with, say, H5 were to develop the ability to infect humans, we'd be up a very thick and sticky creek, because nobody on earth has any immunity to H5 influenza.

Starting in 1997, there have been recurrent outbreaks of an H5 strain (specifically H5N1, with the N designating another protein called neuraminidase, which is less important to infectivity) in domestic and wild birds in Asia, which in at least two countries, Vietnam and Thailand, have infected people. This strain causes very severe disease and has killed young and healthy victims. It has also shown (so far) limited ability to be transmitted from person to person. H5N1 is now firmly entrenched in Asian bird populations and it's showing up in all sorts of unexpected places -- even tigers, which is really novel. Many experts believe it is likely only a matter of time before an H5N1 strain hits on the right combination of mutations to become highly infectious among Homo sapiens, and then, Kapow! -- by which I mean millions of seriously ill Americans (not to mention the rest of the world), severe disruptions to international commerce, an overwhelmed health care system, and, if enough people are sick at once, possible break downs in public services causing all sorts of collateral damage.

Other bloggers are on the case regularly, so that's all I'm going to have to say about this for now. Except that, in conclusion, our wartime President has diverted vast quantities of public health funding and planning to the threat of bioterrorism, which has now become largely synonymous with public health emergency preparedness. This has meant not only immediate misdirection of government resources, but also a cultural blind spot. Nature is still out there folks.

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