The 2024-25 flu season was the highest severity flu season in more than a decade, according to an analysis of US data published last week in Morbidity and Mortality Weekly Report.
The assessment of data from the Influenza Hospitalization Surveillance Network, which covers 9% of the US population, shows that, from October 1, 2024, through April 30, 2025, officials recorded 38,960 flu-associated hospitalizations, for an overall cumulative hospitalization rate of 127.1 per 100,000 population—the highest rate observed since the 2010-11 flu season. The peak weekly flu hospitalization rate of 13.5 per 100,000, reached in early February, also represented the highest weekly rate seen since the 2010-11 season.
Across all age-groups, hospitalization rates during the 2024-25 season were 1.8 to 2.8 times higher than median rates observed from the 2010-11 through 2023-24 seasons. The rate was highest among patients aged 75 and older (598.8) and lowest among those aged 5 to 17 years (39.3). The cumulative flu-associated hospitalization rate among all age-groups was higher than that for COVID-19 or RSV.
Among 10,269 randomly sampled patients hospitalized for flu, 89.1% had one or more underlying medical conditions, 16.8% were admitted to an intensive care unit (ICU), 6.1% received invasive mechanical ventilation, and 3.0% died in the hospital. Just one third (32.4%) had received a flu vaccine, while 84.8% received flu antiviral treatment, though the percentage of children aged 5 to 17 who received antiviral treatment was only 61.6%.
The study authors say flu vaccination and antiviral treatment rates remain suboptimal.
"All persons aged ≥6 months should receive an annual seasonal influenza vaccine," the authors concluded. "All hospitalized patients with suspected or confirmed influenza should receive timely antiviral treatment to reduce the risk for influenza-associated complications."
Another pediatric flu death, 280 total
Meanwhile, current seasonal flu activity remains at very low levels, according to the Centers for Disease Control and Prevention's (CDC's) most recent FluView report.
The overall percentage of emergency department (ED) visits with a discharge diagnosis of flu for the week ending September 6 was 0.2%.
But another pediatric flu death was added to the total for the 2024-25 flu season, which has seen the most pediatric deaths in any non-pandemic flu season since the condition became reportable in 2004. The death, which occurred the week ending February 1 but wasn't reported to the CDC until recently, brings the total for the season to 280 flu-associated pediatric deaths.
COVID-19 may be declining
In other respiratory illness updates from the CDC, COVID-19 wastewater levels are at high or very high levels across the country but may be on their way down throughout the South.
The CDC's wastewater map shows COVID-19 viral activity was high or very high in 27 states for the week ending September 12, primarily in the West but also in parts of the South, Midwest, and Northeast. Only seven states have low or very low levels of COVID-19 in wastewater.
Modeling by the CDC suggests the epidemic COVID-19 trend is declining across the South and growing in the Upper Midwest and Northeast.
Data posted through the week ending September 6 show test positivity for SARS-CoV-2 (the virus that causes COVID-19) is 10.8% and that COVID-19 accounted for 1.5% of ED visits. Both numbers were down slightly from the previous week.
The most recent variant surveillance data show the XFG variant—one of several offshoots of the JN.1 subvariant—accounted for 78% of sequenced samples on August 30.
