When Is Flu Season 2023-2024, and How Intense Will It Be? Virus Experts Share Essential Flu Insights for This Year

Will flu season 2023-2024 be a bad one? Here's what infectious disease doctors want us all to know this year.

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Australia is in the midst of another rough flu season. In summer 2022, Australian public health authorities said the infection rate was on par with 2019: The country’s worst flu season on record. So far it appears 2023 could be similar—plus, confirmed flu cases represent just a fraction of the true total because most people don’t get a laboratory test to confirm that they’re sick.

So, with the 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 2023-2024 flu season up North? 

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Will flu season 2023-2024 be bad?

“We look very closely at Australia,” 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. Thanks to similarities like societal behaviors and areas of population density, flu patterns in the Northern Hemisphere often mirror Australia’s. 

This year’s flu season in Australia hit fast, hard, and early. A total of 18,518 cases were reported in January through March, compared to just 622 cases in the same timeframe last year. Experts say high numbers early in the year can be indicative of a severe season—and offer clues of what’s to come for us this winter. “That being said, it’s not always predictive,” Dr. Maves notes.

For instance, medical professionals warned of a potentially serious flu season last year. “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 last year.” 

As for this year? “We are anticipating a normal 2023-2024 season,” says Linda Yancey, MD, an infectious disease specialist at Memorial Hermann Health System in Houston, TX.  The 2020-2021 season saw almost no influenza because of pandemic precautions—and as predicted, influenza roared back in the 2021-2022 season. It’s since settled back into its pre-pandemic pattern, she explains. 

But there are a few challenges ahead: Covid-19 uncertainties, the resurgence of RSV (respiratory syncytial virus), and the continued post-pandemic delay in exposure to viruses among children. 

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What to expect from the 2023-2024 flu season 

Data from Australia suggests there’s nothing more severe about this year’s flu strain itself: Intensive care admissions and days off for sick leave are similar to previous seasons.

There is one troubling trend—almost 80% of hospital admissions this year have been children under age 16, according to the Australian Government Department of Health and Aged Care.  “It’s a disproportionately higher rate,” Dr. Maves says, possibly due to the pandemic delay in children’s exposure to common, routine respiratory infections

Another explanation? The flu vaccination rate among children aged five to 15 in Australia is just 13.7%, lower than in previous years (and about a quarter of the number of American children vaccinated). Even among Australian adults under age 50, only 20.5% are vaccinated—less than half of the average 50% of American adults who get the flu shot. This coverage could play a role in why the US didn’t get hit as hard by flu season last year compared to Australia. 

Still, these spikes in reported flu cases could also be related to changes in behaviors around testing, Dr. Maves explains. “One interesting thing that came out of Australia is they did actually have a lot more lab-confirmed influenza,” he says. “Everyone’s still looking for Covid—so that means more people are having tests done, and we diagnose [the flu] more.” 

Covid adds another question mark to the upcoming flu season. “We’re still learning what seasonal Covid is going to be like,” Dr. Maves says. “Is it going to gradually attenuate as it’s been doing? Or are we going to have flu seasons with two circulating respiratory viruses—where we have not just the predicted 30,000 annual flu deaths, but maybe a comparable number of Covid deaths on top of it?” 

Covid variants change more rapidly than the flu does, too, he says, which makes it difficult to draw conclusions about how it will develop over time compared with the flu, which is relatively stable year-to-year. “We don’t know, but I’m betting it’s going to be kind of running parallel with the flu.” 

RSV made a sweeping comeback last year as well. Research published in June 2023 in the American Medical Association’s JAMA Health Forum found that RSV’s seasonal pattern changed during the pandemic—last year, 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. The US Food and Drug Administration (FDA) recently approved an RSV vaccine for adults over age 60, but there is still no pediatric vaccine. “It may take a few years for that risk [to children] to normalize again,” Dr. Maves says.

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When does the 2023-2024 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, he says. 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 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.

Here’s what doctors want you to know about the flu in children

Which flu shots are available this year?

Like last year, the flu shots for the 2023-2024 season are “quadrivalent,” meaning they contain four different flu virus 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.

For those under age 65, the CDC does not recommend any one type of flu vaccine over another. “They’re all comparably effective,” Dr. Maves explains. So, whatever’s available at your local pharmacy or doctor’s office is likely to do the trick.

But if you’re over age 65, “three different flu vaccines are preferentially recommended this year because they provide an extra measure of protection in that age group,” Dr. Amler says. These include the Fluzone High-Dose Quadrivalent vaccine, Flublok Quadrivalent recombinant flu vaccine, or Fluad Quadrivalent adjuvanted flu vaccine.

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Should I get the flu shot?

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

Even if you’re not at 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. But 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.”

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Experts recommend getting a Covid vaccine this fall as well. On July 13, US Department of Health and Human Services (HHS) Secretary Xavier Becerra drafted a letter to the US vaccine manufacturers stating that the new Covid vaccine should be available by the end of September, remain accessible at the current distribution locations, and be available at a reasonable cost. “It’s perfectly safe to get the booster at the same time as the flu vaccine,” Dr. Yancey adds.

Along with getting your flu shot, here are expert-recommended ways to stay healthy this flu season

What to do if you get the flu

If you do get sick with flu this season, Dr. Amler says that it’s a good idea to get a Covid-19 test as the symptoms can be pretty similar. But if you are down with the flu, aim to stay at home for about five days after your symptoms begin. “As long as people are feeling better, not running fevers, and it has been five days since the start of their illness, they are considered non-infectious,” Dr. Yancey explains.

You should still get a flu shot if you’re unvaccinated after recovering. 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.

And whether you get sick or not, here’s how to handle awkward flu season etiquette this year.

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Sources
People: Ryan Maves, MD, Professor of Infectious Diseases at Wake Forest School of Medicine and Chair of the COVID-19 Task Force with the American College of Chest Physicians Linda Yancey, MD, infectious disease specialist at Memorial Hermann Health System in Houston Robert Amler, MD, the Dean of 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 Websites: Australian Government Department of Health and Aged Care: “National Notifiable Disease Surveillance System” Australian Government Department of Health and Aged Care: “Australian Influenza Surveillance Report Communicable Disease Epidemiology and Surveillance Section (CDESS) Report no. 05, 2023” FluTracking: “Latest Australian Weekly Report” The National Centre for Immunisation Research and Surveillance: “Influenza vaccination coverage data” US Food & Drug Administration (FDA): “FDA Approves First Respiratory Syncytial Virus (RSV) Vaccine”   Centers for Disease Control and Prevention (CDC): “2023-2024 CDC Flu Vaccination Recommendations Adopted | CDC”  Centers for Disease Control and Prevention: "Flu Vaccines for Children” US Department of Health & Human Services: “Letter to COVID-19 Vaccine Manufacturers” Centers for Disease Control and Prevention: "Influenza (Flu) Key Facts About Flu Vaccine" Journals: JAMA Health Forum: “Seasonality in Respiratory Syncytial Virus Hospitalizations and Immunoprophylaxis” Scientific Reports: "Predicting seasonal influenza epidemics using cross-hemisphere influenza surveillance data and local internet query data"
Medically reviewed by Dr. Arun Chandran, MD, on August 21, 2023

Leslie Finlay, MPA
In addition to The Healthy, Leslie has written for outlets such as WebMd.com, Fodors.com, LiveFit.com, and more, specializing in content related to healthcare, nutrition, mental health and wellness, and environmental conservation and sustainability. She holds a master's degree in Public Policy focused on the intersection between public health and environmental conservation, and an undergraduate degree in journalism. Leslie is based in Thailand, where she is a marine conservation and scuba diving instructor. In her spare time you'll find her up in the air on the flying trapeze or underwater, diving coral reefs.