The U.S. flu season is starting earlier than usual, and hospitals in CDC's surveillance network are already seeing the effects. In its FluView report for week 41, covering the week ending Oct. 17 and released Oct. 23, the Centers for Disease Control and Prevention said: "This is the highest weekly rate for Week 41 since the 2010-2011 season."

That rate comes from FluSurv-NET, a network that tracks lab-confirmed flu hospitalizations in selected counties across the country. It counted 798 flu hospitalizations from Oct. 4 to Oct. 17, a weekly rate of about 1.1 per 100,000 people before adjustment for reporting delays. It is a sample-based rate, not a national count of every hospitalized American.

The good news is that flu activity overall is still low. The practical message is timing: the virus is arriving before many households have scheduled flu shots, and H1N1 seasons tend to fall relatively harder on children and younger adults than H3N2-dominated seasons do.

A Season Running Ahead of Schedule

Clinical laboratories reported 5.7% of respiratory specimens positive for flu in week 41, up from 5.0% the week before and 3.9% in week 39, according to CDC's weekly reports. CDC said seasonal activity is increasing in many parts of the country and is higher than typically seen at this time of year.

The broader measures remain quiet. The share of outpatient visits for flu-like illness was 2.2%, below the national baseline of 2.9%. Hospitals reporting to CDC's National Healthcare Safety Network logged 4,811 flu admissions, about 1.4 per 100,000 people, which CDC described as stable but trending upward. No flu-related pediatric deaths had been reported for the 2026-27 season.

Most states and territories still show minimal outpatient activity, with 48 jurisdictions at the minimal level and two at moderate. But the number of metro areas at moderate activity jumped from eight to 25 in a single week, an early sign of local hot spots.

H1N1 Dominates, and It Carries a New Mutation

The virus mix is unusual — of 241 influenza A specimens subtyped by public health laboratories in week 41, 239 were H1N1, two were H5 and none were H3N2. The week before, labs did find a handful of H3N2 viruses, so H3N2 is circulating at very low levels rather than absent entirely.

Researchers at Northeastern University say the circulating H1N1 carries a mutation known as G155E, first detected in Japan in May. Samuel Scarpino, a professor at Northeastern's Bouvé College of Health Sciences, told Northeastern Global News that "This H1N1 variant appears to be behind the current surge and the early start." Preliminary lab testing suggests this season's vaccine should still recognize the virus, though some teenagers and young adults may have less built-up immunity.

All three components of the 2026-27 vaccine were updated, including the H1N1 strain, according to CDC's season guidance. CDC has not yet published a formal assessment of how well the vaccine matches the mutated virus, and vaccine effectiveness estimates for this season are not available.

An early start does not by itself predict a severe winter. Flu seasons can peak early and fade, or build steadily into January. What remains unknown is whether H1N1 will keep its lead, whether H3N2 or influenza B will rise later, and how much pressure the early wave will put on hospitals.

Bird Flu in Washington Remains a Separate Concern

CDC's week 41 report also listed one confirmed human H5N1 case, in an adult dairy worker in Washington state. Nature World News previously reported on the Yakima County resident who tested positive after exposure to infected cows. The person was not hospitalized, and local and state health officials say the risk to the general public is low.

CDC stressed that human-to-human spread of H5 bird flu has not been identified. Since that report, Washington agriculture officials confirmed an infected dairy herd in neighboring Benton County, bringing the state to about nine affected herds, Capital Press reported. No new human cases had been reported.

The two viruses matter together for one reason — health officials urge farmworkers to get a seasonal flu shot so seasonal and bird flu viruses are less likely to infect the same person, a mix that could in theory let the viruses swap genes.

Shots, Antivirals and Who Should Act First

CDC recommends an annual flu vaccine for everyone 6 months and older, ideally by the end of October. Those at highest risk of complications include adults 65 and older, young children, pregnant people and anyone with asthma, diabetes, heart disease or a weakened immune system. With H1N1 leading, healthy older children and younger adults should not assume they are low risk.

Antiviral drugs work best when started early, so people in high-risk groups who develop fever, cough or body aches should contact a health care provider promptly rather than waiting to see if symptoms pass. Many insurance plans and Medicare Part B cover flu shots, so it is worth checking with your plan, and many pharmacies offer walk-in vaccination. Uninsured adults can check local health departments for low-cost clinics.

The week 42 FluView report, covering the week ending Oct. 24, is expected later this week and will show whether the early climb is continuing. Nature World News will follow the data as it is released.

The bottom line: flu activity is still low nationally, but an H1N1-heavy wave has pushed mid-October hospitalization rates to their highest in more than a decade. Getting vaccinated now is the most practical step, and the key uncertainty is whether this early start turns into a heavier winter.

What Readers Want to Know

Is the flu season starting early this year? Yes. CDC says activity is higher than usual for mid-October, though still low overall, with 5.7% of clinical lab tests positive in the week ending Oct. 17.

What does "highest since 2010–11" mean? CDC's FluSurv-NET hospitalization rate for week 41 was the highest for that week since the 2010–11 season. It is a rate from selected counties, not a total count.

Which flu strain is spreading? Nearly all subtyped viruses are H1N1. No H3N2 was found in week 41 public health lab testing.

Does the flu vaccine protect against this H1N1? Preliminary lab work suggests it should still recognize the virus. Formal effectiveness estimates for this season are not yet available.

Is the Washington bird flu case linked to seasonal flu? No. It is a separate H5N1 infection from dairy cattle exposure, and no human-to-human spread has been identified.

When is the next CDC update? The week 42 FluView report, covering the week ending Oct. 24, is expected later this week.