Early Flu Season Is Here as H1N1 Surges

4 min read

The early flu season reached the U.S. in late August, weeks ahead of a normal year. A changed H1N1 strain now drives most cases, the latest CDC data show.

Key Points

Flu began rising in late August, weeks earlier than usual.
Nearly all flu A cases now come from one H1N1 strain.
Doctors say this year’s shot still gives real protection.

Why This Early Flu Season Stands Out

Most years, flu picks up in late fall and peaks in winter. This year, cases started climbing in late August.

According to the CDC’s weekly flu report, 7.6% of flu tests came back positive in the week ending October 24. At the same point last year, that number sat below 1%.

Hospital visits are rising too. The CDC counted about 6,100 flu hospital admissions that week alone. So far this season, at least 16,000 people have been hospitalized.

The agency also reported the first child flu death of the 2026-27 season. That child had an H1N1 infection.

98.9%of the flu A samples the CDC subtyped in late October were H1N1, according to its weekly flu report.

Meet the Strain Behind the Surge

Last winter, a version of H3N2 called subclade K caused most infections. This fall, a different virus has taken over.

The new leader is H1N1, the same family behind the 2009 swine flu pandemic. Many samples carry a small change called G155E.

Scientists in Seattle first flagged this change in September. As Becker’s Hospital Review reported, it sits on a part of the virus that antibodies use to spot it.

That could make it a little harder for the body to fight off. Early lab tests found that teens and young adults may be less protected.

Have you had your flu shot this season?

Yes, already done
Not yet, but I plan to
I am not sure yet
Not this year

Does Your Flu Shot Still Work?

This is the question many people are asking. The short answer is yes, at least partly.

This year’s vaccine was built in spring, before G155E spread widely. Even so, the CDC found that 94% of tested H1N1 samples still matched the vaccine strain well.

The other two parts of the shot also look like a strong match. The CDC says it is still too early to measure how well the vaccine works this season.

Virologist Andrew Pekosz of Johns Hopkins explained the risk in plain terms to TODAY.

“We may have less immunity, not no immunity,” he said.

Good to know. A vaccine mismatch means less protection, not zero. A flu shot can still lower your risk of serious illness.

Who Should Get Vaccinated and When

The CDC says flu vaccines are for everyone aged 6 months and older. You can read the full details on the CDC 2026-27 flu season page.

Experts usually suggest getting the shot by the end of October. However, a shot in November still helps, especially with the season starting early.

Your body needs about two weeks to build protection. That means a shot now could cover you before Thanksgiving travel begins.

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How to Protect Yourself This Fall

A vaccine is the best first step, but it is not the only one. Simple daily habits also slow the spread.

The CDC’s everyday prevention guide lists washing hands and covering coughs. It also tells sick people to stay home.

If you do get sick, call a doctor quickly. Flu antiviral medicines work best when started within two days of the first symptoms.

Book a flu shot if you have not had one
Wash your hands often with soap and water
Cover coughs and sneezes with a tissue or your elbow
Stay home when you feel sick
Call a doctor within two days of flu symptoms

What Happens Next

Doctors are watching the season closely. Some expect a second wave later in winter once the H1N1 wave peaks.

“I think it is just starting earlier,” said Dr. Bernard Camins of Mount Sinai.

Shorter days are here too, since clocks moved back on Sunday, as our daylight saving time story explains. More time indoors often means germs spread more easily.

For more updates like this, visit our Health section.

This article is for information only and is not medical advice. Please talk to a doctor about your own health.