Flu Season Update: What to Expect in Spring 2026

As winter transitions into spring, concerns about the ongoing 2025-2026 influenza season remain. Even as initial trends showed a decline in cases, experts are closely monitoring a potential resurgence, particularly with the emergence of influenza B strains. Here’s a comprehensive look at the current state of the flu season and what individuals can do to protect themselves.

Current Flu Activity and Trends

The latest data indicates that flu activity, while decreasing isn’t over yet. The Centers for Disease Control and Prevention (CDC) reports that all flu vaccines for the 2025-2026 season are trivalent, protecting against three key strains: an A(H1N1) virus, an A(H3N2) virus, and a B/Victoria lineage virus [CDC].

Initially, influenza A viruses dominated the early part of the season. However, a second wave of influenza B cases is now emerging and is expected to persist through the spring months [Fox News]. This pattern aligns with historical trends, where influenza A typically appears first, followed by influenza B.

As of February 10, 2026, 27 states are reporting “very high” or “high” levels of flu activity [Today]. Approximately 18% of flu tests are currently returning positive results, a slight increase from two weeks prior, though still a significant decrease from the 31% seen at the finish of December [Today].

The Role of Influenza A H3N2 Subclade K

This year’s flu season has been marked by a modern influenza A H3N2 variant, known as Subclade K. This strain has proven particularly challenging due to the population’s limited pre-existing immunity and decreased vaccination rates [Fox News]. The current vaccine has also demonstrated reduced effectiveness against this specific strain.

Vaccination and Prevention

Health officials continue to emphasize the importance of annual flu vaccination as the best way to reduce the risk of infection and severe complications [CDC]. The CDC recommends seasonal flu vaccination for children, pregnant women, and adults, with single-dose formulations of thimerosal-free vaccines being prioritized [CDC].

FluMist, the live attenuated influenza vaccine, is now approved for self- or caregiver administration [CDC]. FluBlok, the recombinant influenza vaccine, has been approved for use in individuals ages 9 and older, expanding its eligibility from the previous age limit of 18 years and older [CDC].

Severe Cases and Hospitalizations

Monitoring of emergency room visits reveals a decrease in admissions and hospitalizations for respiratory syndromes compared to the same period last season. Cases of severe and complicated influenza are also down compared to the previous season, with A(H1N1)pdm09 being the most common subtype in severe cases. Importantly, the majority of severe cases occur in unvaccinated individuals.

Key Takeaways

• The 2025-2026 flu season is extending into the spring months.
• Influenza B cases are increasing, following an initial wave of influenza A.
• The H3N2 Subclade K variant presents a challenge due to limited population immunity and reduced vaccine effectiveness.
• Annual flu vaccination remains the most effective preventative measure.
• Severe cases are predominantly occurring in unvaccinated individuals.

As the flu season continues to evolve, staying informed and taking preventative measures are crucial. Healthcare providers play a vital role in supporting patients in making informed decisions about vaccination and protecting their health.