The Year Without Germs Changed Kids

In the spring of 2021, Brett Finlay, a microbiologist at the University of British Columbia, offered the world a bold and worrying prediction. “My guess is that five years from now we are going to see a bolus of kids with asthma and obesity,” he told Wired. Those children, he said, would be “the COVID kids”: those born just before or during the height of the crisis, when the coronavirus was everywhere, and we cleaned everything because we didn’t want it to be.

Finlay’s forecast isn’t unfounded. As James Hamblin in last year, our health relies on a constant discourse with trillions of microbes that live on or inside our bodies. The members of the so-called microbiome are crucial for digesting our food, training the immune system, even greasing the wheels of cognitive function; there does not seem to be a bodily system that these tiny tenants do not in some way affect. These microbe-human dialogues begin in infancy, and the first three or so years of life are absolutely pivotal: Bacteria must colonize babies, then the two parties need to get into physiological sync. Major disruptions