Flu Is Still Raging. Can You Get It Twice In One Season?

The United States is currently facing the worst flu season in over 15 years, with cases surging in most states. Over 33 million Americans have gotten sick this season so far, and elevated flu activity is expected to continue in the coming weeks, experts say.

In early February, doctor visits and hospitalizations for flu hit the highest levels since the 2009-2010 flu season, during the height of the swine flu pandemic, according to the U.S. Centers for Disease Control and Prevention’s latest FluView report.

The 2024-2025 flu season, which has caused an estimated 19,000 deaths so far, is now classified by the CDC as “high severity.”

In the U.S., flu season typically starts in October and peaks between December and February. However, the timing and severity varies from year to year. The 2024-2025 flu season got off to a slow start and appears to be the most intense in over a decade. It coincides with surges of COVID, norovirus, and respiratory syncytial virus, which has been dubbed a “quad-demic.”

As this flu season rages on, you may be wondering if it’s possible to get flu twice in the same season. If you’ve already recovered from the flu, can you get it again and do you still need a flu shot? We spoke to experts to find out.

Can you get flu twice in one season?

Yes, you can get the flu twice during the same season, experts say.

“Overall, it’s possible but not incredibly likely,” Dr. Geeta Sood, assistant professor in the division of infectious diseases at Johns Hopkins University, tells TODAY.com.

Reinfection can happen because multiple strains of influenza are circulating during any given season — this why the annual flu shot includes three or four different strains.

There are four types of flu viruses (A, B, C and D), and subtypes or strains of each — which can mutate. Influenza A and B cause seasonal epidemics every winter, per the CDC.

Right now, the predominant strains circulating in the U.S. are flu A H1N1, flu A H3N2, and one influenza B strain. Over 95% of flu cases right now are influenza A, per the CDC.

“However, smoldering along is influenza B, and the B strains usually become more prominent toward the end of the flu season,” Dr. William Schaffner, professor of infectious diseases at Vanderbilt University School of Medicine, tells TODAY.com.

“So it is possible for someone to get influenza A and then a month or so later, get influenza B,” says Schaffner.

After you recover from the flu, you’ll have some immunity against the strain of the virus you were infected with because the body develops antibodies that recognize and neutralize the virus to protect against future infection, per the CDC.

“You don’t get lifelong immunity to flu after you get infected, but you get pretty good immunity for a while,” Dr. Edmund Milder, pediatric infectious disease specialist at Rady Children’s Hospital-San Diego, tells TODAY.com.

Immunity from natural infection is thought to last around six months, depending on the person, but it can wane fairly quickly, says Sood.

Additionally, immunity against one strain of the flu may not protect you against another. “There is very little, if any, cross-protection from your antibodies from (influenza) A to B,” says Schaffner. “There will be some cross-protection among two influenza A strains, for example, H1N1 and H3N2,” Schaffner adds.

So, can you get flu A or flu B twice in one season? Theoretically, yes. “It would be possible if you are unlucky enough to get it right at the start and are exposed to the same virus at the tail end of a long flu season and don’t have enough protection,” says Milder.

If you do get the same type of flu twice, it’ll probably be caused by different strains, says Milder — for example, you recover from H3N2 then contract H1N1. “It’s unlikely that you get the exact same strain of influenza twice in one season,” Milder adds.

Who is more likely to get flu twice in one season?

Some groups may be at higher risk of reinfection.

One such group is people who did not get the flu shot, the experts say. If an unvaccinated person gets the flu, they’ll only develop antibodies against that strain, instead of having antibodies against the three or four strains included in the flu shot.

People ages 65 and over, children under 2 and people with weakened immune systems or underlying conditions are also more vulnerable, the experts note.

“If you are older, frail or immunocompromised, your immune system is not going to protect you as well after you’ve had a first infection, so those people are going to be more likely to get the second infection,” says Schaffner.

Individuals who have a lot of contact with other people are also at higher risk. “Flu viruses tend to spread pretty effectively in congregate settings, where people are close together,” says Milder. These include schools, nursing homes and health facilities.

“If you are a person who’s always out and about, you’re going to expose yourself more frequently,” Schaffner adds.

How to tell if it’s flu or another virus

While it is possible to get flu twice in one season, if you develop respiratory virus symptoms after already recovering from the flu, it’s more likely that you caught a different circulating illness, such as COVID-19, RSV, adenovirus, rhinovirus, parainfluenza and more, the experts say.

“The problem is it’s almost impossible to tell them apart,” says Sood. Many of these viruses cause similar symptoms, such as a sore throat, cough, fever, runny nose and a headache.

Flu does have some characteristic signs, such as severe body aches and a higher fever, but there’s still a lot of overlap, says Sood.

The only way to know if you have influenza is by getting a diagnostic test from a health care provider, Schaffner adds.

Testing is important because it can allow for prompt treatment. “We have medications that might help, especially if you’re high risk,” says Milder. These include flu antivirals such as Tamiflu, which are most effective when taken within 48 hours of symptom onset.

Is it too late to get a flu shot?

“No, it’s not too late, and I would recommend getting the flu shot if you haven’t gotten it so far,” says Milder.

Even if you’ve already had the flu, you can still benefit from vaccination “because of those other influenza strains out there,” says Schaffner.

The 2024-2025 flu vaccines protect against three viruses: influenza A H1N1, influenza A H3N2 and an influenza B strain.

Significant flu activity, including surges of influenza B, can continue as late as May — so getting the flu shot now can offer protection for months.

“(The flu shot) is not perfect. You can still get the flu, but we know flu vaccination decreases hospitalizations, serious illness and death,” says Milder.

You can also protect yourself from the flu by avoiding contact with sick people, wearing a mask in crowded indoor spaces and washing your hands frequently.