I recently wrote a review of a great book that I am re-reading these days: 1491: New Revelations of the Americas Before Columbus. And today I realized that it might contain an explanation for something that has recently rocketed to the top of the news: swine flu in Mexico.
Right now there is open speculation as to why some people are getting infected and others are not, why some people are getting very sick and others not. Some reports suggest more people in Mexico are getting more seriously infected than eslewhere. And here's where 1491 comes in.
Author Charles Mann reviews all manner of resarch as to why some diseases had such a devastating effect on Indian populations. One factor was human leukocyte antigens or HLAs, an important part of the body's disease fighting systems. Humans fight disease better when they have a diversity of HLAs.
Most human groups have a "scatterbox mix" of HLAs but South American Indians have fewer HLA types than populations in Europe, Asia, and Africa. In South America, according to one estimation, the minimum probability that a pathogen in one host will next encounter a host with a similar immune spectrum is about 28 percent. By comparison, in Europe the chance is less than 2 percent.
Now I'm sure that I'm over-simplifying here, but it would seem that there's an infection differential of 14X in there somewhere. While the population of Mexico is, in broad terms a mix of Europeans and Indians, it may well have less HLA diversity than the population of a melting pot like the United States. Which bodes well for the States, not so well for Mexico. I hope the World Health Organization is checking this out.