Do coronavirus countermeasures appear to crush ordinary flu infections?
The Centers for Disease Control reported in September that steps taken to slow the spread of the coronavirus appear to have a dramatic effect on transmission of ordinary flu.
"Influenza virus circulation declined sharply within two weeks of the COVID-19 emergency declaration" in the U.S., the CDC said. After March 1, 2020, the CDC reports that lab tests confirming flu cases declined by 98% from earlier in the U.S. winter. During the summer, it said positive influenza testing in the U.S. reached a historical low, decreasing from less than 20% to 2.3%. The CDC observed the same trends in data from other Northern Hemisphere countries and in tropical regions. It noted that during their winter "Southern Hemisphere temperate climates have had virtually no influenza circulation," adding that "the consistent trends over time and place are compelling and biologically plausible."