Flu Season Is Ending in the U.S. Why That Matters.

Is flu activity decreasing in the United States?

For once, I have some genuinely good news to share. Flu activity in the United States is finally tapering off. The CDC’s FluView surveillance system, which aggregates syndromic and lab-based surveillance data from across the country, reports that visits for flu-like illness are now below 2 percent. This is a clear indication that the worst of the season is behind us. We’re also seeing a continued drop in flu hospitalizations and the percentage of tests coming back positive. All of this points toward a steady decline, consistent with the pattern we expect during this time of year.

Why does flu season happen in the winter?

What I’ve always found interesting—and often overlooked by people outside of public health—is that this pattern, while reliable in temperate places like the U.S. with cold winters and dry air, does not hold true around the world. In tropical regions, for example, flu doesn’t follow a single, predictable curve. Instead, flu has multiple small peaks throughout the year. And here’s the other detail I think more people need to understand. The flu season we experience in the Northern Hemisphere is often shaped by what’s already happened in the Southern Hemisphere months earlier, particularly in Asia and Oceania, where many new flu strains first emerge.

Why the End of Flu Season Still Matters

While the decrease in flu activity is welcome news, it’s also a key moment to reflect on what we’ve learned and what comes next. Public health experts rely on global data to track and prepare for future influenza threats. Here are the most important things to understand about flu season timing, surveillance, and risk.

1. Flu Season in the U.S. Follows a Predictable Pattern

In temperate regions like the U.S., flu season typically begins in fall and peaks during the coldest months. The virus thrives in cold, dry air and spreads more easily indoors, where people gather closely.

2. Tropical Countries Have Year-Round Flu Activity

Unlike in the U.S., tropical regions experience multiple smaller flu outbreaks throughout the year. This unpredictability makes continuous monitoring essential in those areas.

3. Global Flu Trends Shape the U.S. Season

The strains that circulate in the U.S. often originate in the Southern Hemisphere. Monitoring outbreaks in countries like Australia and regions of Asia provides early warning for North America.

4. Surveillance Systems Are the Backbone of Flu Response

Tools like CDC’s FluView collect data from hospitals, labs, and clinics to monitor illness levels and detect emerging strains. This data guides public health decisions, vaccine formulation, and response planning.

5. Vaccines Depend on Global Coordination

Twice a year, the WHO reviews global flu data to recommend which strains should be included in the seasonal flu vaccines. This process relies on accurate, real-time data from dozens of countries.

6. The End of Flu Season Is Not the End of Surveillance

Even as cases drop, public health officials continue to collect and analyze data. This ongoing work ensures we’re not caught off guard by unusual strains or early surges.

7. Better Flu Surveillance Helps Prepare for Future Pandemics

Influenza surveillance isn’t just about seasonal flu. It also plays a critical role in detecting potential pandemic strains—making it a vital part of global health security.

How is flu tracked in the U.S. and globally?

This is why robust, global surveillance matters so much. When I first started working internationally for CDC back in 2003, many countries were still struggling to justify investing in flu surveillance. With other, more visibly deadly diseases like HIV and tuberculosis demanding attention, flu often seemed like a lower priority. But without reliable data, you’re flying blind. You can’t prepare vaccines effectively, and you miss early warnings about dangerous strains. The U.S. flu season might be over, but the work of tracking and preparing for the next one never stops. It’s the type of work in public health—quiet, rigorous, systematic disease surveillance—that goes unnoticed but is vital to our health security.