Flu Season Surges to Record Highs in the U.S.

The United States is currently experiencing a severe flu season, with doctor visits for flulike illnesses reaching the highest levels in nearly 30 years, according to data from the Centers for Disease Control and Prevention (CDC). This surge is occurring alongside the circulation of a new influenza A strain, raising concerns about vaccine effectiveness and overall public health.

Record-Breaking Flu Activity

In the week ending December 27, 2025, almost one in ten people visiting a doctor in the U.S. – over 8 percent – presented with flulike symptoms [Scientific American]. This is the highest rate recorded since the CDC began tracking such data in 1997. Nationwide, 8.2% of outpatient doctor’s visits were for flu-like illnesses [CBS News].

Impact and Severity

So far this flu season, the CDC has reported over 120,000 hospitalizations and 5,000 deaths attributed to influenza, including nine pediatric fatalities [Scientific American]. Approximately 4,700 people die annually from the effects of the flu [Scientific American]. As of January 5, 2026, 48 jurisdictions were reporting “high” or “very high” levels of flu activity [CBS News].

New Strain and Vaccine Effectiveness

A new variant of the influenza A strain, H3N2, known as subclade K, is believed to be driving the increased infections [Scientific American]. This variant carries mutations that may reduce the effectiveness of this year’s flu vaccine. However, the RIVM states that the vaccine protects “about as well as in other years” [Scientific American].

Monitoring Respiratory Illness Activity

The CDC monitors respiratory illness activity using the acute respiratory illness (ARI) metric, which captures a broader range of diagnoses than previous measures like influenza-like illness (ILI) [CDC]. Wastewater surveillance is also being used to detect traces of infectious diseases in communities, providing an early warning system for potential increases in infections [CDC].

Vaccination and Prevention

Even as approximately 130 million doses of the flu vaccine have been administered this year [CBS News], vaccination rates are lower than in previous years. The CDC recently updated its recommended childhood vaccine schedule, emphasizing “shared clinical decision-making” with doctors for children not considered high-risk [CBS News]. Vulnerable populations, including those aged 60 and over, individuals with lung disease, and people with diabetes, are particularly at risk and are encouraged to get vaccinated [Scientific American].

Looking Ahead

The full impact of the post-holiday travel period on flu rates remains to be seen, and rates of doctor visits and hospitalizations could continue to rise. Continued monitoring of the evolving influenza strains and vaccination efforts will be crucial in mitigating the spread of this severe flu season.