It’s a mystery that has puzzled the world’s virologists.
The United States and Western Europe — home to many of the planet’s best doctors and hospitals and the most robust public health infrastructures — have been among the regions hit hardest by the novel coronavirus.
Some have speculated that climate, population demographics, government response (or lack thereof), and other factors can explain the high numbers of infections in the developed world. And there is probably some truth to each of these hypotheses. But none seems to fully explain why half of the countries that make the top 10 in Covid-19 deaths per capita — a top 10 that includes the United States — are also among the wealthiest and most medically advanced in the world.
Heenam Stanley Kim, PhD, is a professor and microbial geneticist at Korea University in Seoul. He has his own hypothesis — one that has to do with the bacteria that live in the human gut. “Evidence accumulated around the world [suggests] that people who have an altered gut microbiota have a higher risk for serious Covid-19,” he says.
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The human gastrointestinal tract is home to trillions of bacteria, often collectively referred to as the gut microbiota or microbiome. The types, numbers, diversity, and proportions of these bacteria vary from person to person. While some species reliably populate the guts of healthy people and are therefore regarded as “good” or helpful, other types tend to be more numerous in the guts of those who are unwell. The presence of unhealthy bacteria is also associated with barrier problems in the lining of the intestines — a condition known as leaky gut.
In a recent paper, Kim makes the case that gut dysbiosis — the term microbiologists use to describe an unwell or out-of-whack microbiome — may allow the novel coronavirus to penetrate the gut’s lining, called the epithelium. “When…