According to CDC data, the total number of flu cases in the United States is declining, leading experts to wonder if this year's relatively mild flu season is coming to an end.
CDC's data shows that for the week ending in Feb. 12, 1,324 new influenza cases were reported by clinical laboratories, down from 1,506 cases the week before, and down from a peak of 6,894 for the week ending in Dec. 25, 2021.
However, while cases have been dropping steadily since the week ending Jan. 1, influenza hospitalizations reported to HHS have risen recently.
According to CDC data, influenza hospitalizations peaked at 2,616 during the week ending Jan. 1 and began declining over the following four weeks. However, hospitalizations rose from 785 for the week ending Jan. 29 to 993 for the week ending Feb. 5, and 1,073 for the week ending Feb. 12.
The 2020-21 flu season was an exceptionally mild one, which many experts credit to Covid-19 precautions taken during the year, including social distancing and masking. As a result, experts were concerned about what this year's flu season might look like, as a previously mild flu season could cause flu immunity to wane, the Associated Press reports.
In early November, an influenza outbreak at the University of Michigan, where over 700 cases were reported, was found to have been caused by a strain of the flu known as Type A H3N2, which typically causes higher rates of hospitalizations and deaths, especially among the elderly, AP reports.
However, while that strain became dominant throughout this flu season, case numbers have overall remained comparably low, something Edward Belongia, a flu expert at the Marshfield Clinic Research Institute, found surprising.
"We have occasionally seen other very mild flu seasons, but not where H3N2 is the dominant strain," he said. "That's what really makes it odd."
Angela Branche, an infectious disease specialist at the University of Rochester, agreed that this year's flu season has been unusual.
"I don't have any [flu] cases in my practice this week," she said. Typically, doctors in the Rochester, N.Y. area would have around 50 to 100 flu cases a day this time of year, AP reports.
And while flu cases are declining, the abnormally low number of cases is causing experts to wonder whether this year's flu season is coming to an end—or if there will be a future surge.
"The question we're asking ourselves now is: 'Is this it, or is there more to come?'" CDC's Lynette Brammer said. As Covid-19 cases continue to decline, behaviors like mask-wearing are likely to change, which could cause a rise in other respiratory viruses, including influenza, Brammer said.
CDC data so far suggests that around two-thirds of people testing positive for the flu are children and young adults. In the past, children have driven the spread of influenza, so "it's quite possible we could see continued increases," Brammer said.
And while it seems like this year's flu season is "easing to the finish line," according to William Schaffner, an infectious disease expert at Vanderbilt University, he added, viruses are often unpredictable.
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