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Flu cases plummeted during the 2020-2021 season, CDC says

Flu sick
Posted at 1:01 PM, May 24, 2021

With social distancing measures in place due to the COVID-19 pandemic, confirmed cases of influenza plummeted during the 2020-2021 flu season.

According to data published on the CDC's website, U.S. clinical health labs and public health labs reported just 2,124 confirmed flu cases between Sept. 27, 2020 and May 15, 2021 (though the true number of people who contracted the flu was likely higher).

Those 2,124 cases represent an extreme decline in the spread of the flu compared to the 2019-2020 season. Between October 2019 and April 2020, the CDC estimated that at least 39 million people contracted the flu.

It wasn't just the U.S. The World Health Organization says that worldwide flu cases also fell to minuscule levels during the 2020-2021 flu season.

It's clear that social distancing and universal mask mandates impacted the plummeting levels of flu cases in the winter of 2020 and 2021. Data from the CDC shows that patients visiting doctor's offices for influenza-like illnesses plummeted in March and April of 2020 and have remained low ever since.

Flu chart

But while decreased levels of flu cases may seem like a welcome sign, it's in some ways left doctors in the dark on how they plan to handle the next flu season.

Scientific American reports that each year's flu vaccine is based on strains of influenza that have been circulating the previous season. In February, the WHO made recommendations for next year's vaccine but was forced to do so on much less information than they have in previous years.

While there are concerns that the flu vaccine may not be as effective next season, doctors are hopeful that less spread in 2020-2021 meant there was less of a chance for mutated streams, which would keep vaccines effective.