Flu season has taken off nationwide, with cases rising rapidly in some parts of the country over the past few weeks.
Flu Season Overview
The Centers for Disease Control and Prevention (CDC) released its latest report on Friday, estimating that so far this season, there have been at least 4.6 million illnesses, causing more than 49,000 hospitalizations and 1,900 deaths. “We’ve seen sustained, elevated activity across multiple key indicators in many areas of the country,” said Alicia Budd, head of the CDC’s domestic influenza surveillance team.
The report also highlighted that young children-infants through age 4-have been hit hardest so far.
Wastewater Surveillance Signals Early Surge
From November to December, wastewater concentrations of influenza type A rose 390 % nationwide, according to data from WastewaterSCAN, an academic program through Stanford University in partnership with Emory University. “We’re not yet seeing any sign of plateauing,” said Marlene Wolfe, program director for WastewaterSCAN and an assistant professor of environmental health at Emory.
The upward trend is increasing “very consistently,” a pattern that suggests the virus is spreading faster than expected.
Hospitalization and Death Data
The CDC’s latest numbers show more than 49,000 hospitalizations and 1,900 deaths nationwide. While the report lists only three pediatric flu deaths so far this year, state health officials have reported additional cases. For example, a child in Wisconsin died of flu, and the North Carolina Department of Health and Human Services reported its first pediatric flu death on Wednesday. Those cases are likely not counted among the CDC’s latest report, which is current through December 13.
The 2024-2025 flu season was particularly deadly for children. According to the latest data, 288 children died of flu-tying a record set during the 2009-2010 H1N1 pandemic. A CDC report published in September found that half of the children who died of flu last year were otherwise healthy, and about 89 % hadn’t received the flu vaccine.
Geographic Spread
Flu activity is high or very high in 14 states, including Colorado, Idaho, Louisiana, Michigan, New Jersey, and South Carolina, as well as New York City, Washington, D.C., and Puerto Rico, according to the CDC report. While the CDC’s latest report shows “minimal” flu activity in Wisconsin, state health officials reported a child’s death there.
Dominant Strain and Vaccine Concerns
Influenza A, specifically H3N2, is the dominant strain right now. While anyone of any age can be affected, H3N2 tends to cause more hospitalizations and deaths in older adults. “We’ve had past seasons where there have been what we call drifted viruses, which is how we would categorize this subclade K,” said Budd. “In some of those instances, there have been impacts on vaccine effectiveness, but there have also been seasons with drifted strains where we’ve seen the vaccine continue to provide protection.”
The annual flu shot is notoriously imperfect when it comes to matching the exact strains that circulate. This year, a strain called H3N2 subclade K emerged, making changes on the surface protein of the virus. The surface protein is important because that’s what the body looks for to recognize whether it’s seen the virus before. If the protein looks even slightly different, the body may not be able to fight it off as well.
Budd said it’s hard to predict how well this vaccine will ultimately work. Even though the strain has “drifted” a bit, the vaccines do contain protection against H3N2 virus in general. “It is still the primary preventive measure against flu, severe illness, and we absolutely continue to recommend it this year, even in light of the drifted strain,” she said.
Antiviral Use Trends
Demand for Tamiflu, an antiviral used to help treat the flu, is slightly higher than it was this time last year, according to GoodRx. “What stands out this season is how early Tamiflu use is climbing,” said Tori Marsh, senior director of research for GoodRx. “When we see prescription antiviral use rise sooner than average, it often points to flu activity building earlier and potentially lasting longer.”
Key Takeaways
- Flu season has surged to 4.6 million cases, 49,000 hospitalizations, and 1,900 deaths nationwide.
- Wastewater data shows a 390 % rise in influenza A, signaling early and aggressive spread.
- Children are the most affected group, with 288 deaths and 89 % of deceased children unvaccinated.
The CDC’s next flu update will release on December 30, so public health officials and the public will need to stay alert as the season progresses.
Closing Thoughts
With schools on break and family gatherings on the horizon, the risk of transmission to older adults remains high. The CDC and health experts urge everyone, especially children, to get vaccinated and to consider early antiviral treatment if symptoms appear. The combination of surveillance data, hospital reports, and vaccine guidance underscores the importance of staying proactive during this intense flu season.
