(NEXSTAR) – Flu cases are surging across the country – more than half of states are now at “very high” levels, the most severe designation by the Center for Disease Control and Prevention – but is it possible that some of those people are catching it for a second time?
Flu is an illness caused by influenza viruses that often arrives suddenly with symptoms of fever, cough, headaches, sore throat and more. “Flu can cause mild to severe illness, and at times can lead to death,” according to the CDC.
There are four types of flu (A, B, C and D), but the annual “flu season,” typically starting in October and lasting as long as March or April, is caused by the viruses behind Flu A and Flu B. Flu A also has two subtypes that routinely circulate, H1N1 and H3N2.
As for getting the flu twice in once season, Dr. Amesh Adalja, an infectious disease expert at Johns Hopkins Center for Health Security, tells Nexstar that it is indeed possible.
“You could get influenza [A] and then get influenza B, yes,” Adalja said. “Or you could get infected very early in the season, and then by the end of the season your immunity wears off, so yes you can get infected more than once.”
Influenza A is by far the dominant type this year, making up 2,642 of the 2,693 lab-confirmed cases of flu during the fourth week of 2025. Within each of the main flu types, there are multiple strains, and the viruses continue to mutate.
Because of this, Cleveland Clinic Infectious Disease Specialist Dr. Donald Dumford says its possible to contract influenza A, for example, twice in one season.
“If you got H1N1 first, then I expect you would be well protected for the H1N1 strain for the next several months,” Dumford said. “You could still get infected with another strain like H3N2.”
Is it the flu or another virus?
Unfortunately, influenza shares a number of symptoms with respiratory viruses like COVID-19 and RSV, so it can be difficult to know which virus is making us miserable.
To know definitively you’ll want to be tested shortly after you start feeling symptoms, which often include a scratchy/sore throat, runny nose and fever. If the lab result comes back positive, there are antiviral drugs that can be taken to shorten the sickness and lessen the symptoms. While a local medical provider can administer the test, Dumford noted that this year are also tests available over the counter at pharmacies.
The CDC recommends starting antiviral drugs such as oseltamivir, commonly known by the brand name Tamiflu, within one to two days after flu symptoms begin.
“I always like to reiterate that if you have the flu, stay home from work or school and isolate yourself from your family as much as possible until fever free for 24 hours (without fever reducing medications) and your symptoms are starting to improve,” Dumford told Nexstar. “Even then, I’m a proponent of masking for the next several days after you are out of isolation.”
Cleveland Clinic doctors recommend doing the following to help prevent the spread of flu:
- Proper handwashing.
- Avoiding touching your eyes, nose and mouth.
- Avoiding people who are sick.
- Wearing masks in situations when you can’t avoid people who are sick, such as caring for a sick child.
