Out of Africa

We have all become amateur epidemiologists, and I frankly thought there would be hell to pay when the Covid epidemic finally reached Africa. According to a news article by journalist Linda Nordling of Cape Town South Africa, writing in Science, Africa

seems to have weathered the pandemic relatively well so far, with fewer than one confirmed case for every thousand people and just 23,000 deaths. Yet several antibody surveys suggest far more Africans have been infected with the coronavirus—a discrepancy that is puzzling scientists around the continent.

A more technical article by Moustapha Mbow and colleagues, much of which I thought I understood, led to a similar conclusion. Several explanations have been proposed, including the simple fact that Africans are on the whole younger than, say, Europeans and Americans. The explanation may also be genetic. Another hypothesis, however, is that Africans are infected with various parasites, which ramp up their immune systems so that they can effectively fight new pathogens. Mbow and colleagues cite the “hygiene hypothesis” and suggest that

early and chronic exposure to pathogens leading to relentless immune cell activation in harsh environments induces a strong regulatory immune response to counteract excessive inflammation.

Before I give succor to any anti-vaxxers, let me state that this hypothesis in no way militates against vaccinating for measles, mumps, chickenpox, pertussis (or whooping cough), polio, or all the other deadly childhood diseases that were commonplace when I was in grade school and do not appear every hundred years or so.

A day or so after my physician advised me to get a flu shot, I ran across two articles, one by reporter Kelly Servick in Science and another by reporters Lesley Wroughton and Max Bearak in the Washington Post. These articles noted that there has been almost no flu season in South Africa this year, and the Post quoted Cheryl Cohen of South Africa’s Institute for Communicable Diseases to the effect that

The main explanation is that measures against coronavirus are having an impact on flu transmission.

That explanation, if it holds up, will be good news to those who are concerned about a flu epidemic piggybacked on top of the current Sars epidemic. It would be better news if the United States were taking stronger measures against the coronavirus, but God forbid I should make a political statement like that.