When Is Flu Season 2025-2026, and How Intense Will It Be? Virus Experts Share Essential Flu Insights for This Year

It may be too early to fully know what to expect for the 2025-2026 flu season, but experts look down under for clues about what may lie ahead for virus season in the United States.

“We look very closely at Australia,” says Ryan Maves, MD, an infectious disease and critical care physician at Atrium Health Wake Forest Baptist. Thanks to similarities like societal behaviors and areas of population density, flu patterns in the Northern Hemisphere often mirror Australia’s. 

Data from Australia’s National Notifiable Diseases Surveillance System show that flu cases began rising earlier than usual this year—a trend that continued from last season. In the first quarter of 2025, nearly 48,500 influenza cases were reported, up from about 30,000 during the same period in 2024, contributing to what the Royal Australian College of General Practitioners calls a “record-breaking” flu season.

So, with the flu virus flat out like a lizard drinking down under—that’s Aussie slang for working hard and fast—should we brace ourselves for a challenging 2025-2026 flu season here in America?

Will flu season 2025-2026 be bad?

Pre-pandemic, a high level of flu cases early in the year generally indicated a rough season ahead. While Australia’s recent flu seasons have begun earlier than usual, experts note that illness severity has remained lower than in pre-pandemic years, even with higher case counts.

Frank Esper, MD, a board-certified pediatric infectious diseases specialist at Cleveland Clinic Children’s explains that the COVID-19 pandemic “significantly disrupted the circulation of many respiratory viruses.” He adds that winter viruses such as influenza and RSV—which often overlapped with COVID surges—saw sharp declines and noticeable shifts in their usual seasonal patterns.

Still, medical professionals worldwide warned of a potentially serious flu season in 2022–2023—the virus season that coincided with the official end of the pandemic and its restrictions. “But it turned out to be kind of typical,” Dr. Maves says. On average, there are about 30,000 deaths and half a million hospitalizations due to the flu in a normal season. “That’s what we saw,” he says.

As for this year? While it’s still too early to know for sure, Dr. Esper says that flu circulation has largely returned to normal over the past two years—meaning plenty of viral activity is expected this fall and winter, but nothing out of the ordinary.

One new challenge, however, is that the U.S. government shutdown has paused national respiratory virus surveillance. Federal reports tracking influenza, COVID-19, and RSV haven’t been updated recently, even as virus activity rises. Without coordinated data, states may not get the full picture of how these infections are spreading, which could complicate response efforts heading into colder months.

What to expect from the 2025-2026 flu season 

One big difference between Australia and the U.S. is the flu vaccination rate. While vaccination coverage in the U.S. is below optimal (the U.S. Office of Disease Prevention and Health Promotion aims for a target of 70%), flu vaccination rates tend to be higher across most age groups in the U.S. than in Australia—with one exception: older adults, where Australia leads.

According to the U.S. Centers for Disease Control and Prevention (CDC), flu vaccine coverage for last year (2024-2025) is estimated at:

• 49.2% for children aged 6 months to 17 years
• 46.7% for adults over age 18
• 48.3% for adults 65 and older

Comparably, the National Center for Immunisation Research and Surveillance in Australia estimates its 2025 flu vaccination coverage at:

• 25.7% for children aged 6 months to 5 years
• 14.5% for children aged 5 to 15 years
• 20.8% for people aged 15 to 50 years
• 32.3% for adults aged 50 to 65 years
• 60.5% for adults over age 65

These vaccination rates may help explain why Australia is seeing such high flu activity this season. While last year’s flu season in the U.S. was worse than expected, experts don’t anticipate that the 2025–2026 season will be any more severe.

CDC data show that the 2024–2025 flu vaccine was about 40% to 55% effective in preventing flu-related hospitalizations among adults. Hareesh Singam, MD, infectious disease specialist at the Cleveland Clinic and adjunct professor at the University of Minnesota, notes that the prior year’s flu vaccine offered a similar level of protection, reducing hospitalizations by about 41% to 44%.

“It’s important to remember that [the flu shot] does not 100% ‘prevent’ the flu,” says Jason E. Zucker, MD infectious diseases specialist at NewYork-Presbyterian/Columbia University Irving Medical Center. But it’s absolutely still worth getting your jab. “While the flu shot may reduce your risk of illness, its biggest benefits are that it reduces how sick you will get—[meaning your] severity of symptoms—and it decreases your risks of complications, including hospitalization and death.” 

COVID during the 2025-2026 flu season

COVID also presents a bit of a curveball for flu season predictions. “We’re still learning what seasonal COVID is going to be like,” Dr. Maves says. He says that COVID variants change more rapidly than the flu does, making it difficult to conclude how it will develop over time compared with the flu, which is relatively stable year-to-year.

Unlike the flu, COVID has continued to circulate throughout the summer months over the past few years.

Continues Dr. Maves: “The problem during winter is that we could have simultaneous influenza and COVID-19 seasons, neither of which might be that bad in isolation but having a major impact on public health when combined.” Two major respiratory viruses in circulation can spell trouble: “[We could have] not just the predicted 30,000 annual flu deaths, but maybe a comparable number of COVID deaths on top of it.”

Dr. Singam recommends that people who are immunocompromised or have COPD or other respiratory diseases still wear masks in crowded areas. “Masks can help reduce the risk of transmission of not only COVID but influenza as well,” he says.

RSV during the 2025-2026 flu season

RSV has also made a sweeping comeback. Research published in June 2023 in the American Medical Association’s JAMA Health Forum found that RSV’s seasonal pattern changed during the pandemic—in 2022, RSV season was continuous, with highly unusual spikes occurring during the summer months. Again, the virus hit children especially hard.

While RSV is often fairly mild in healthy adults, it can be dangerous in older adults and younger kids. In 2023, the U.S. Food and Drug Administration (FDA) approved an RSV vaccine—initially for adults over 60, as well as for pregnant women and infants.

According to current CDC recommendations, adults 75 and older should receive a one-time RSV vaccine, while adults ages 50 to 74 who are at higher risk are also encouraged to get vaccinated. Pregnant women should receive the Abrysvo RSV vaccine between 32 and 36 weeks of pregnancy, ideally from September through January, to help protect their newborns after birth. Infants under eight months without maternal protection should receive nirsevimab or clesrovimab for added defense against RSV.

“Several papers are pending on the [RSV] vaccine’s impact,” Dr. Singam says. However, he points to clinical trials that show the effectiveness of the RSV vaccine in adults is between 83% and 89% during the first RSV season after vaccination. 

When does the 2025-2026 flu season start and end?

In general, flu season in the U.S. lasts from October to as late as May, peaking between December and February. “I would expect influenza to be typical this year,” Dr. Esper says, noting that the highest activity is likely to occur between December and February.

Although Australia experienced an early rise in flu cases this year, the official vaccination recommendations from the CDC remain the same—September and October are still the best months for most people to get vaccinated, with a few exceptions:

• Pregnant women in their third trimester can get a vaccine in July or August (or as soon as it’s available) to ensure their babies are protected from the flu after birth.
• Children who need two doses of the flu vaccine should get their first dose as soon as it’s available.
• Older adults (65 and older) and pregnant women in their first or second trimester should wait until September or October to vaccinate unless directed by their doctor. 

Which flu shots are available this year?

Like last year, this season’s flu vaccines target one fewer strain than they did in the past.

Flu shots over the past decade have been “quadrivalent,” meaning they contain four different flu virus strains—two influenza A strains and two influenza B strains, explains Robert Amler, MD, MMS, MBA, FAAP, FACPM, dean of the School of Health Sciences and Practice at the Institute of Public Health at New York Medical College.

According to a 2024 briefing published in the journal Nature, precautions taken during the COVID pandemic—such as mask-wearing, social distancing, and attention to better ventilation—eliminated one of the influenza B strains from circulation. 

As a result, vaccine manufacturers began shifting to “trivalent” flu vaccines in the 2024–2025 season. For 2025–2026, all U.S. flu shots will continue to use this three-strain formula, which includes two influenza A subtypes (H1N1 and H3N2) and one influenza B lineage (B/Victoria), says Dr. Esper.

He notes another important update this year: the CDC’s Advisory Committee on Immunization Practices (ACIP) has recommended the removal of thimerosal, a mercury-based preservative, from all U.S. influenza vaccines. Thimerosal was previously used in a limited number of multi-dose vials to prevent contamination, but manufacturers are now transitioning entirely to single-dose vaccine packaging to meet this new guideline.

Similar to last year, the CDC has not recommended any one type of flu vaccine over another for those under age 65. “They’re all comparably effective,” Dr. Maves explains. So, whatever’s available at your local pharmacy or doctor’s office will likely do the trick.

But if you’re over age 65, the CDC typically recommends a “high-dose” flu vaccine for extra protection, Dr. Amler says. 

Should I get the flu shot?

The flu vaccine is not 100% effective at preventing the flu, but it greatly lowers the risk of contracting a bad case or developing serious complications, Dr. Maves says. This is particularly important for people with chronic health conditions.

Even if you’re not considered high-risk, getting your flu shot is still important. “Many of us don’t have chronic lung disease, don’t smoke, are generally healthy,” Dr. Maves explains. “But unless you live in some extraordinary bubble, you have a parent, a grandparent, a child, a friend, someone you work with who does fit into one of those [high-risk] categories.” By getting your flu shot, you improve their protection, along with your own.

He points to the rubella vaccine as a similar example. This infection causes mild or no symptoms in most people, so getting vaccinated isn’t necessarily about protecting your own health. However, the disease can lead to devastating complications in newborns. “So all of us are vaccinated against rubella so that pregnant women don’t get it, preventing catastrophic birth defects,” he says.

Experts recommend getting a COVID vaccine this fall as well. Dr. Singam also recommends patients with special circumstances—such as those who are pregnant, without a spleen, or have plans to travel—talk to their doctors about additional vaccines that may be recommended.

Remember: It’s generally safe to receive both the flu and COVID vaccine simultaneously, Dr. Maves adds. In fact, “There are trials of combined influenza and COVID-19 vaccines in a single injection,” he says. “Hopefully, this will simplify and thus improve vaccination rates for both.” 

What to do if you get the flu

If you do get sick with flu-like symptoms this season, it could still be a good idea to get a COVID-19 test. There are no longer special recommendations in place for COVID, explains Shira Doron, MD, chief infection control officer for Tufts Medicine and hospital epidemiologist at Tufts Medical Center. But if you’re someone who is at high risk for complications of respiratory viruses—and therefore would qualify to receive treatment with Paxlovid for COVID or Tamiflu for influenza—“you should test at the first sign of symptoms since those drugs work best when given early,” Dr. Doron says. 

Dr. Zucker adds that testing also offers valuable information that can guide prevention strategies. “It can help you make better decisions about when to visit friends or family members who may be more susceptible to severe disease—like those who are older, immunosuppressed, or have multiple medical problems.” 

But whether you test positive for COVID or the flu, Dr. Zucker says you can return to normal activities when your symptoms have been improving overall for at least 24 hours and you do not have a fever. Last year, the CDC simplified its COVID recommendations to align with those of other respiratory viruses—which means no more five-day isolation periods after symptoms subside.

Still, it’s a good idea to take some added precautions such as practicing good hand hygiene, wearing masks, and practicing physical distancing, especially when around other people indoors, Dr. Zucker says. 

Once you’re feeling better, you should still get a flu shot if you’re unvaccinated. There is the chance you can catch a different strain of the virus, and you don’t get the same “cross-protection” from having the flu as you get from the vaccine.

For daily wellness updates, subscribe to The Healthy by Reader’s Digest newsletter and follow The Healthy on Facebook and Instagram. Keep reading:

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