Tuesday, March 18, 2003

This is really scary.

I haven't commented on the mystery Asian illness yet on this blog, mainly because I have been busy on some other things. Steven Den Beste has some thoughts. In particular, he comments that it seems clear that it is influenza. This surprises me not at all. Like Steven, when I heard "Guangdong Province, China" my immediate conclusion was that we had an influenza outbreak on our hands. It looks like the virus is more contagious but less deadly than the 1997 virus, although these sorts of things can still change as diseases mutate further. Therefore, there are reasons to be at least a little worried.

Steven comments that new strains of influenza normally come from China, normally because most influenza strains come from birds (particularly chickens) and the way that chickens, ducks, and pigs are kept in China leads to the creation of new viral strains. Essentially, pigs get infected with both chicken and human viruses, the DNA of the two viruses combine together, and then the new combined virus infects a human. (This can then mix DNA with a human virus that is already present in the person that is infected. The nightmare scenario normally involves an extremely deadly but not very contagious form of the virus spreading into the human population, then combining with a very contagious strain that is already present in some human, and then an extremely deadly and contagious strain causing a worldwide epidemic. This is why the actions taken in 1997 in Hong Kong were so extreme. An extremely deadly but not very contagious strain of influenza was present in the chicken population, which infected a small number of people, killing several of them. The entire chicken population of Hong Kong and nearby was killed, in order to reduce the chance of someone already sick with another influenza virus being infected).

I think that Steven's blaming it on Mao's collective farms might be excessive, however. The tendency for new strains of influenza to come from China is clearly older than collectivised farms. (It always seems to be Guangdong, too, not just China. The 1918 virus that killed between 20 and 40 million people appears to have originated there as well, as indeed does the 1889 virus). It may be that it is something to do with Chinese traditional practices that have been incorporated into the collective farms. Having pigs, chickens, and people living close together is pretty common throughout all of South East Asia as well as China, but the influenza outbreaks don't seem to come from Java, for instance. It may just be the density of birds and animals in that region is very great, or it may be that particular types of influenza viruses just happen to be endemic in the birds of that region, although I would expect that even bird viruses would spread around the world fairly quickly. (I need to try and find some agricultural statistics, I suppose, and finding accurate ones from places like China and Indonesia is going to be very hard).

Update: I have read in several places in the news media that the disease is "probably not influenza", without any explanation whatsoever as to why it is probably not influenza. Along with that, all these stories have given lots of circumstantial evidence that would tend to suggest that it is influenza. Can anybody explain to me what the media's justification is for saying that it is probably not flu.

Further Update: Patric Crozier asks a question as to whether people in China have built up resistance to influenza. I am not an expert on the subject, but I believe the answer is "no more than anybody else". Firstly, influenza spreads rapidly, so even if new strains originate in China, they don't necessarily infect Chinese people in general more than anybody else. A strain gets into the human population, and it gets all round the world pretty quickly. (In 1918, this apparently took about three months). Influenza is a virus that mutates a lot, and although it is possible to build up resistance to specific strains of it, it is very difficult to develop resistance to influenza in general. (This is why there is a new flu shot every year. Vaccine manufacturers build a vaccine for those strains that are in circulation at the start of winter, and hope that no new strains come along too quickly. You are encouraged to get a flu shot every year not because the previous year's innoculation has worn off, but because this years disease is different). (The innoculation appears to be longlasting. Very unusually, the 1918 virus was most lethal amongst people in their 20s and 30s, and older people were much less affected by it. A widely (but by no means universally) held theory as to why this is so is that an epidemic of a genetically similar but much less lethal influenza had infected the world thirty to forty years previously, and older people therefore had resistance that younger people did not). So, essentially, the Chinese are probably resistant to many strains (like the rest of us) but vulnerable to new strains.

Influenza is a complicated disease. Infection with one strain gives resistance to genetically similar strains, but not to strains which are genetically too different. (This is why you can get a different influence vaccination every year. Early cases are looked at, conclusions are reached as to what type of virus will be prevalent this year, and people are vaccinated for that type of virus. A different type will be prevalent the next year, so the previous year's vaccination becomes useless.

Even further update: Okay, it's fairly clear by this point that it isn't influenza, although it may be something else that has arrived in people via pigs, chickens and/or ducks in much the same way. We still don't quite know how serious it is, or whether it could still mutate into something more contagious or virulent. Still, some people are not not as concerned as others. I'm still at least a little worried, however.

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