As temperatures have dropped, more activities have moved indoors, where the Covid virus tends to spread. But I mentioned Canada above — along with the cold-weather parts of the U.S. where caseloads were not rising a month ago — for a reason. If the weather were really the dominant cause, the recent Covid patterns would look different. As unsatisfying as this is, the full explanation for the surge remains unclear. We offer tidy explanations for the virus’s ups and downs — like weather, school calendars, mask habits, even sporting events — when reality is messier.

Source: New York Times November 24, 2021 01:08 UTC