Influenza B Is Making a Comeback—Here's Why It Matters Now

Influenza B activity is increasing nationally for the second consecutive week, even as influenza A cases decline. According to the CDC's latest surveillance report for the week ending January 31, 2026, while overall flu activity remains elevated across the United States, the virus landscape is shifting in ways that could affect how you protect yourself and your family in the coming weeks.

Why Is Influenza B Suddenly Rising?

For most of this flu season, influenza A(H3N2) viruses have dominated the scene, accounting for the vast majority of cases. However, the CDC's most recent data shows a notable change: influenza B is now increasing nationally and in most regions of the country, while influenza A activity is decreasing. This shift is significant because the two viruses behave differently and can require different response strategies.

The timing of this increase matters. We're now in early February, which means flu season still has several weeks of potential activity ahead. Influenza B tends to peak later in the season than influenza A, so this upward trend could indicate that the overall flu season may not be winding down as quickly as some hoped.

What Does This Mean for Vaccination and Protection?

The good news is that the flu vaccine protects against both influenza A and B strains. The CDC estimates that approximately 134 million doses of influenza vaccine have been distributed across the United States this season, and vaccination remains one of the most effective tools for reducing your risk of infection and serious complications. Since influenza B is now increasing, ensuring you're vaccinated—if you haven't been already—becomes even more relevant.

The data on vaccination effectiveness this season is sobering. Among children who were eligible for flu vaccination and had known vaccination status, approximately 90% of reported pediatric deaths this season occurred in children who were not fully vaccinated against influenza. This underscores why vaccination is particularly critical for vulnerable populations, especially children.

How Severe Is This Season Overall?

The CDC classifies the 2025-2026 flu season as moderate in severity across all ages, but the picture is more complex when you break it down by age group. Here's what the current severity assessment shows:

• Pediatric Severity: Children aged 0-17 years are experiencing high severity, with the highest peak weekly hospitalization rate observed since the 2010-2011 season.
• Adult Severity: People aged 18-64 years are classified as having moderate severity, with hospitalization rates remaining elevated but not at the highest levels.
• Older Adult Severity: Adults aged 65 years and older are also classified as having moderate severity at this point in the season.

The overall impact has been substantial. The CDC estimates that there have been at least 22 million illnesses, 280,000 hospitalizations, and 12,000 deaths from flu so far this season. The weekly influenza-associated hospitalization rate peaked during Week 52 at 12.8 per 100,000 population, marking the second highest peak weekly rate overall since the 2010-2011 season.

What Should You Do If You Get Sick?

Beyond vaccination, there's another tool available: prescription flu antiviral drugs. These medications can treat flu illness and should be started as early as possible, especially for patients at higher risk for flu-related complications. If you develop flu symptoms—fever, cough, body aches, or fatigue—contact your healthcare provider promptly to discuss whether antivirals might be appropriate for you.

The rise in influenza B cases doesn't change the fundamental protective strategies, but it does reinforce their importance. With several weeks of flu season remaining and a new surge in B-strain cases, now is the time to ensure you and your family are vaccinated if you haven't been already, and to be prepared to seek early treatment if illness develops.