Did you get the flu last winter? If so, you were one of at least 34 million people in the United States who got sick during what the Centers for Disease Control and Prevention deemed a “moderately severe” flu season. Those cases resulted in at least 15 million medical visits, 380,000 hospitalizations and 17,000 deaths.
This year could be similar, experts predict, and fortunately the flu shot is well-matched to the strains likely to circulate.
Flu Trends from the Southern Hemisphere
We can anticipate what flu season in the United States might be like by looking at the flu season that just ended in the southern hemisphere, says UNC Health pulmonologist and critical care specialist Subhashini Sellers, MD.
“In the southern hemisphere, the seasons are switched, so they’ve just gone through their winter,” Dr. Sellers says. “It’s not a perfect predictor, but their data helps us to understand the current strains and transmission.”
Most countries saw moderate levels of flu, comparable to previous years, though there were a few exceptions. Chile and Zambia saw very high rates of the flu, with multiple strains circulating at once, and a few countries saw high levels of flu-related hospitalizations. Many countries reported their flu season starting earlier than previous seasons.
In the southern hemisphere, the dominant strains were H3N2 and H1N1. Both of these strains are influenza A viruses, and they were also dominant during last year’s flu season. Dr. Sellers says there was a lesser amount of influenza B virus circulating during the southern hemisphere’s flu season; influenza B can cause more severe outcomes in children.
Good news: These strains were anticipated in the creation of this year’s flu shots.
“The current influenza vaccination is a trivalent vaccine protecting against three strains—H3N2, H1N1 and a strain of B,” Dr. Sellers says. “This vaccine is reasonably well-matched to these strains, and the CDC estimates that severe outcomes from the flu can be reduced by 30 to 50 percent with the vaccine.”
Anticipating the 2024-2025 Flu Season
Last flu season marked a return to pre-COVID-19 flu patterns, with activity peaking between late December and late February and petering out by mid-May, rather than peaking early or lasting into summer as it had in the years immediately after the pandemic.
But don’t be surprised if you start to notice friends or coworkers getting the flu at the end of October and beginning of November—that’s when the increase tends to begin.
Still, it’s not possible to predict when cases will peak: “In the past, it has varied widely,” Dr. Sellers says.
Of course, flu is not the only respiratory virus circulating during fall and winter. As in previous years, the coming months will be shaped by COVID-19 and RSV, or respiratory syncytial virus.
“With a combination of these three viruses, hospitalizations will probably be similar, or maybe a little better, compared to last season,” she says.
That prediction is subject to change, though.
“If there is a new strain of a respiratory virus, such as a new COVID-19 variant, that could impact hospitalizations,” Dr. Sellers says. The current COVID-19 vaccine is protective against the latest known strains.
The hospitalization rate is also dependent on people getting their flu shot.
“The more people without a flu vaccine, the higher transmission there will be in the community,” Dr. Sellers says. “With more infection, there’s more hospitalization and more severe disease outcomes.”
Protect Yourself from the Flu and Other Respiratory Viruses
Getting a flu vaccine will help to reduce your risk of getting sick from the flu as well as your risk for serious complications. It’s recommended that everyone over the age of 6 months get a flu vaccine every year.
The CDC recommends that you receive a flu shot by the end of October so that you’ll be protected when cases start to rise, and it’s important to remember that it can take at least two weeks after immunization to provide protection.
Still, “it’s never too late in the season to get a vaccine,” Dr. Sellers says. “We have seen infections persist through late April and early May.”
If you’re 65 or older, or if you’re younger than 65 but have had an organ transplant, ask your doctor about the Fluzone high-dose vaccine, which provides additional protection against the flu. If you’re pregnant or over the age of 60, your doctor may also recommend the RSV vaccine, and the CDC recommends that everyone older than 6 months get a 2024-2025 COVID-19 vaccine.
In addition to vaccinations, there are tried-and-true ways to minimize the spread of disease.
“Make sure you keep up on good hand hygiene, which protects you and reduces transmission,” Dr. Sellers says. “You could also consider wearing a mask during travel or in crowded indoor spaces. We saw during the first year of the COVID-19 pandemic that wearing a mask reduced the transmission of all other respiratory viruses, including influenza.”
Questions about the flu or other respiratory infections? Talk to your doctor or find one near you.