Here’s How Early the Flu Has Struck This Year
Hospitalization data points to how the flu season is kicking into high gear much earlier than in seasons past.
Averaging across seasons, weekly hospitalization rates typically reach or exceed 1.0 per 100,000 population just before the year’s end, or around MMWR week 50, according to data from the CDC.(GETTY STOCK IMAGES)
A look at historical data shows the 2022-2023 flu season is off to a dramatic start, with the weekly hospitalization rate 20 times higher than at the same time last season.
The Centers for Disease Control and Prevention tracks flu hospitalization rates using the Influenza Hospitalization Surveillance Network, which currently collects data from more than 70 counties across 13 states and represents nearly 30 million people, or 9% of the U.S. population. The CDC typically lists rates reflecting cases from early October to late April of the following year, reporting figures for each “MMWR week.” The surveillance network’s dashboard reports weekly hospitalization rates from the 2009-2010 through the 2022-2023 seasons, except for the 2020-2021 season, when there was extremely low flu activity amid the COVID-19 pandemic.
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Why the Flu Season Could Be Severe ]Averaging across those seasons, weekly hospitalization rates typically reach or exceed 1.0 per 100,000 population just before the year’s end, or around MMWR week 50. They generally peak near the start of the following year, at around 5 hospitalizations per 100,000 people on average – though seasons can vary greatly in intensity. After reaching a peak, rates typically drop back down below 1.0 by about four months into the new year.
But that’s not always the case, and this season has been a notable outlier: The weekly rate surpassed 1.0 per 100,000 by week 43, marking a much earlier rise that otherwise hasn’t occurred since the 2009-2010 season over a decade ago. For week 48 this season, or the week ending Dec. 3, the data reflects a hospitalization rate of 5.9 hospitalizations per 100,000 people. That’s down slightly from a week earlier, but still past the average historical peak and a figure about 20 times higher than this time last season, when the rate sat at 0.3. The CDC does note that the 2021-2022 flu season was extended into June due to later influenza activity.
At the same time, while the weekly hospitalization rate was higher earlier during the 2009-2010 flu season, the rate back then also peaked at 4.0 hospitalizations per 100,000 people and subsided greatly before the end of the year. This season, rates for the most part have steadily increased in recent weeks heading into the holidays, when many people will travel and gather indoors with family.
With the flu, RSV and COVID-19 all circulating, Dr. Rochelle Walensky, the CDC’s director, recently encouraged people to wear “a high-quality, well-fitting mask to prevent the spread of respiratory illnesses,” as well as vaccinations.
On top of the early start, experts already were worried that low immunity levels and the relaxing of COVID-19 mitigation measures could fuel a severe flu season in the U.S. The CDC estimates there have been at least 13 million illnesses, 120,000 hospitalizations and 7,300 deaths overall this flu season, which also has seen disparate hospitalization rates impacting some communities of color the most.
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