As the United States enters the new year, seasonal influenza activity remains elevated and continues to increase nationwide, according to the latest influenza surveillance update from the Centers for Disease Control and Prevention (CDC). For Week 51 of the 2025–2026 season (ending December 20, 2025), multiple surveillance indicators showed sustained upward trends across outpatient, emergency department, and hospitalization data, while severity metrics remain relatively low to date. Influenza A(H3N2) viruses continue to predominate. Nationally, clinical laboratories reported that 25.6% of respiratory specimens tested positive for influenza, a sharp increase from the prior week. Percent positivity rose in all ten US Department of Health and Human Services (HHS) regions, ranging from 34.9% in Region 8 to 10.8% in Region 9. Influenza A viruses accounted for 94.7% of all positive clinical specimens reported during the week.
Outpatient respiratory illness increased in parallel. Data from the US Outpatient Influenza-like Illness Surveillance Network (ILINet) showed that 6.0% of outpatient visits were for influenza-like illness (ILI), exceeding the national baseline of 3.1% for the third consecutive week. ILI activity increased across all age groups and all HHS regions, reflecting widespread circulation of respiratory viruses, including influenza, SARS-CoV-2, and respiratory syncytial virus (RSV).
Hospitalizations continued to rise across multiple surveillance systems. The Influenza Hospitalization Surveillance Network (FluSurv-NET) reported a weekly influenza-associated hospitalization rate of 6.2 per 100,000 population, up from 4.4 per 100,000 the previous week. The cumulative hospitalization rate reached 18.2 per 100,000, representing the third highest cumulative rate at this point in the season since 2010–2011, following the 2022–2023 and 2023–2024 seasons.
Among hospitalized patients with influenza A subtype data available, 87.4% were infected with A(H3N2) and 12.6% with A(H1N1)pdm09. Hospitalization burden remained highest among adults aged 65 years and older (53.4 per 100,000), followed by children aged 0–4 years (21.5 per 100,000). Age-adjusted hospitalization rates were highest among non-Hispanic Black persons (35.9 per 100,000), followed by American Indian or Alaska Native persons (20.9), Hispanic persons (16.5), non-Hispanic White persons (14.4), and Asian and/or Pacific Islander persons (8.5).
Additional hospital data from the National Healthcare Safety Network (NHSN) showed 19,053 laboratory-confirmed influenza-associated hospital admissions nationally during Week 51, with admission rates increasing in all HHS regions. Long-term care facility surveillance indicated a hospitalization rate of 22.9 per 100,000 residents, with increasing trends observed in most regions.
Mortality indicators increased modestly. Preliminary data from the National Center for Health Statistics showed that .5% of deaths during Week 51 were attributed to influenza, up from the prior week. CDC also reported five influenza-associated pediatric deaths during the week, bringing the season total to eight pediatric deaths. All reported pediatric deaths were associated with influenza A viruses, predominantly A(H3N2).
Virologic surveillance from public health laboratories showed that 97.3% of reported viruses were influenza A, with 91.8% of subtyped viruses identified as A(H3N2). Genetic characterization indicated that 89.5% of sequenced A(H3N2) viruses belonged to subclade K, similar to prior weeks. CDC estimates that, to date this season, influenza has caused at least 7.5 million illnesses, 81,000 hospitalizations, and 3,100 deaths nationwide.
