The 2025-26 flu season has been brutal, so far.
At least 19 million Americans have had it, and it's not over yet. Flu season typically runs through May, so there's still a good chance of getting the virus.
In today's Vital Signs, Dr. David Winter, an internal medicine specialist with Baylor Scott & White, says flu tends to follow a certain timeline for how long you're contagious, but it can vary.
Dr. Winter: Typically it's contagious the day before you have symptoms. Now, not really contagious, not highly contagious, I should say.
It's worse the second day. Typically, the flu starts and you'll be pretty sick pretty quickly and the second day is when the viral spreading is at its peak and then it starts to decline over the next five to six days.
Baker: You have come up with like a common timeline for the flu?
Dr. Winter: Right, it usually lasts about five days, sometimes six or seven days. And typically, it peaks on the second day of when you're sick and then starts to go down. So, by the end of the week, usually you're fine. And usually by the end of the week you're not contagious.
Baker: So, day one through three is when you get those symptoms. You really begin to feel bad and then what? Day four through five or four through seven, that's when it begins to ease off.
Dr. Winter: That's true, and usually for most folks about day five, you start to feel better. In fact, if at day five you've had no fever for 24 hours, assuming you haven't taken a flu-reducing medicine, if you've no fever, then you're not contagious at that point.
When the fever goes away for 24 hours, you're starting to improve. Even if you have a lingering cough, feel a bit fatigued, at that point you're probably not contagious.
Baker: So, is it safe to go back to work or back to school at that point?
Dr Winter: It is, yes indeed.
Baker: So, it doesn't hang around after the fever has passed?
Dr. Winter: It doesn't for healthy people.
Now, if you're immunosuppressed, if you're taking chemotherapy, if your immune system is not up to snuff, if you're old and frail, sometimes very, very young kids, they can have it linger longer than that, but for most folks by day five or six, you're really not contagious and you're ready to get back into the crowd, back into your routine.
Baker: At what point during all of this should you see a health care provider?
Dr. Winter: Yeah, that's a good question because there is good medicine out there to treat this. Does everybody need it? Not necessarily.
If you had a flu shot, I can tell you, you're likely to have a very mild case if you get it at all. So, if your symptoms are mild, you can stay at home and take over-the-counter medications for cough, for congestion, for muscle aches, for fever. That can work well. But if your systems are pretty significant, that is when you may want to talk with your doctor.
Baker: Which brings up the question: How can you tell if you have or think you have flu or COVID-19 or RSV or just a plain common cold?
Dr. Winter: It can be tricky. The symptoms tend to be similar.
However, with influenza, with the flu, typically they come on more suddenly. You'll have a sudden onset of marked fatigue, high fever, muscle aches, cough.
With common cold, with RSV, with COVID, you may have those similar symptoms, but they usually are less so, come on, more gradually. So, it's hard to tell.
If you're not really sure and you think you need treatment. You have to get a test. And there are good tests available in the doctor's office. You can get a kit from the pharmacy, do a swab of your nose. I would do one for flu and COVID. And if that's positive, then you know you have it. If it's negative, you're probably fine.
Baker: All that said, I think all that said how can we protect ourselves against the flu?
Dr. Winter: The most important thing is the flu shot. It does work. It may not prevent you from getting the flu, but it'll keep you out of the hospital. You'll have a mild case, if at all.
Now on top of that, most of the flu virus is spread through the air. So, be careful when you're in crowds, be careful around people coughing or sneezing.
You can get it from contact, though. If somebody who has influenza touches a doorknob and you touch that doorknob and then rub your nose, you got influenza there.
You have to be careful also with touching. Wash your hands frequently. Many people don't wash their hands good enough. It's interesting because it takes 20 seconds to get all the virus and bacteria particles off your hands. Now that's maybe a long time. I tell people, count to 20 slowly. Oh, here's another way. Sing "Happy Birthday" twice in a row. And that's usually about 20 seconds.
RESOURCES:
How long are you contagious with the flu? A day-by-day timeline
10 things to know about this year's surprisingly fierce flu season
Information for the Flu Season
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