When Is Flu Season 2024-2025, and How Intense Will It Be? Virus Experts Share Essential Flu Insights for This Year

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It’s a little early to know what to expect for the 2024-2025 flu season, says Ryan Maves, MD, professor of infectious diseases at Wake Forest School of Medicine and chair of the American College of Chest Physicians’ Covid-19 Task Force. But experts look down under for clues about what may lie ahead for virus season in the US. “We look very closely at Australia,” Dr. Maves says. Thanks to similarities like societal behaviors and areas of population density, flu patterns in the Northern Hemisphere often mirror Australia’s. 

According to the Australian Centre for Disease Control, flu cases reached an unseasonably early peak this year—the number of confirmed cases recorded by late April spiked 40% compared to the same period last year. 

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 2024-2025 flu season up North? 

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Will flu season 2024-2025 be bad?

Pre-pandemic, a high level of flu cases early in the year generally indicated a pretty rough season ahead. But while Australia’s 2024 flu season started earlier than prior years, Dr. Maves says it was similar last year—and yet, “clinical severity was lower than pre-pandemic levels despite high case counts.” 

He explains that the Covid-19 pandemic disrupted some of the usual seasonality of our other common respiratory viruses like influenza and RSV.

For instance, 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.” 

As for this year? While it’s still too early to tell, experts believe that the flu is more-or-less settling back into its normal patterns—which still means plenty of viral activity going around in the fall and winter, but nothing too far out of the ordinary. 

But a few possible challenges lie ahead: ongoing Covid-19 uncertainties, the resurgence of RSV (respiratory syncytial virus), and the emergence of an avian flu in the US, in addition to the re-emergence of tuberculosis and meningitis.

What to expect from the 2024-2025 flu season 

One big difference between Australia and the US is the flu vaccination rate. While vaccination coverage in the US is below optimal (the US Office of Disease Prevention and Health Promotion aims for a target of 70%), it’s still much higher than in Australia. 

According to the US Centers for Disease Control and Prevention (CDC), flu vaccine coverage for last year (2023-2024) is estimated at:

• 53.9% for children aged 6 months to 17 years
• 48.5% for adults over age 18
• 50.6% for adults 65 and older

Comparably, the National Center for Immunisation Research and Surveillance in Australia estimates its 2024 flu vaccination coverage at:

• 20% for children aged 6 months to 5 years
• 11.8% for children aged 5 to 15 years
• 18.1% for people aged 15 to 50 years
• 29.7% for adults aged 50 to 65 years
• 57.4% for adults over age 65

These vaccination rates could explain why Australia is experiencing an uptick in flu-related hospitalizations as their 2024 winter progresses—while experts don’t expect the US flu season to be more severe than usual this year. According to Hareesh Singam, MD, infectious disease specialist at the Cleveland Clinic, last year’s flu vaccine was about 41% to 44% effective in preventing flu-related hospitalizations. 

“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.” 

Still, while we can’t know for sure what’s in store for the 2024-2025 flu season, a major concern among public health experts is the recent emergence of avian influenza (H5N1) in cattle in the US, explains Dr. Maves. “The reported human cases have been mild in general, although there has been a recent death from the very similar H5N2 influenza in Mexico.” The US cases of H5N1 have occurred mainly among agricultural workers exposed to cattle and poultry, emphasizing the need to maintain vigilance for disease surveillance in our farm animals as well as in the people who work on those farms. “It’s a very important reminder of the interplay between animal health and human health,” says Dr. Maves. “It’s important to protect our food supply, and it’s important to protect the health of the people who work to ensure that supply.”

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. There has been a small uptick in total cases recently, which may be related to summer travel, Dr. Maves says. 

“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.” 

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. Last year, the US Food and Drug Administration (FDA) approved an RSV vaccine for adults over age 60—and it’s been recently approved for infants and pregnant women as well.

“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 2024-2025 flu season start and end?

In general, flu season in the US lasts from October to as late as May, peaking between December and February. “I think this year’s flu season is going to be like last year, where we started seeing it in October, peaking in January, and tapering off over the course of the rest of the winter until about April,” Dr. Maves says. 

Australia had a very striking early spike in their hospitalization rates this year. Still, the official vaccination recommendations from the Centers for Disease Control and Prevention (CDC) have not changed—September and October are the best times for most people to get vaccinated, with some 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?

One major difference in this year’s flu season? Globally, we’re dealing with one less strain of the virus.

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, the Dean of the School of Health Sciences and Practice at New York Medical College and a former Chief Medical Officer at the CDC Agency for Toxic Substances and Disease Registry.

According to a 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. 

According to the CDC, this means that the US is transitioning to “trivalent” flu vaccines for the 2024-2025 flu season. The FDA is currently working with vaccine manufacturers to ensure timely development, approval, and availability of this year’s flu shots, and the CDC’s recommendations for using these vaccines across various age groups are expected to be released in August. 

Based on past year’s guidance, 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. Again, more guidance will be available from the CDC later this summer. 

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.”

Experts recommend getting a Covid vaccine this fall as well. Dr. Singam says we should expect an updated Covid vaccine ahead of the upcoming winter season that targets the latest variants in circulation.

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. This year, the CDC simplified its Covid recommendations to align with those of other respiratory viruses—which means no more 5-day isolation periods after symptoms subside. Still, it’s a good idea to take some added precautions such as good hand hygiene, masks, and 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.

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