Virtually every article about the swine flu notes epidemiologists’ and public health experts’ struggle to find out why the same virus seems so much more virulent in Mexico than it has been, at least to date, in other countries. Frustratingly, though, we never hear that they’ve made much progress in coming up with a clear answer — though it’s frequently suggested that the quality of the data coming out of Mexico is poor.
This article from the Journal suggests not a single answer but an overlapping series of factors explaining the difference. The suggested factors include pervasive under-reporting of infection (making the mortality rate appear higher), substandard health care and pervasive misdiagnosis in the early stages of the outbreak and even the high altitude and air pollution in Mexico City, which according to the article is normally responsible for a high rate of throat and chest infections. Of course, another possible factor is that it’s gone on several weeks longer in Mexico. And the same virulence will become evident in other countries.
To be clear, these explanations aren’t put forward as conclusive — more along the lines of educated guesses or working hypotheses. Being far from any area of expertise and on a topic so weighty, I don’t want to speculate more. But if you’re interested in the topic, I recommend that you read the piece.
Late Update: The San Francisco Chronicle has another take on the question.
