How Long Is the Flu Contagious?

We all know the flu can spread like wildfire.

Case in point: If you lived in the same house as someone with the flu during the 2021 to 2022 flu season, you had a 50 percent chance of contracting the virus yourself, according to a January 2023 ‌JAMA‌ study.

So if you or someone you know is sick, exactly how long does the contagious period last? Though it’s hard to pinpoint a precise answer, there are some general guidelines to keep in mind to help stop the spread. Here’s what you should know.

The flu is a viral respiratory illness that’s mainly spread by close contact with an infected person, according to the Centers for Disease Control and Prevention (CDC).

People with the flu expel tiny, germ-filled droplets when they cough, sneeze or even talk. When those droplets land in the mouth or nose of another person, they’re at risk for becoming infected too.

The droplets can also land on surfaces (like doorknobs, TV remotes or keyboards, for example). If a healthy person touches the infected surface and then touches their mouth, nose or eyes, they could get sick.

You can’t always avoid these droplets when you’re around someone with the flu. But there are steps everyone can take to help prevent the virus from spreading. The CDC recommends you:

• Avoid close contact with people who are sick, and limit contact with others when you’re sick.
• Cover coughs and sneezes with a tissue, and throw the tissue in the trash when you’re done with it.
• Wash your hands often with soap and water. Use an alcohol-based hand sanitizer when soap and water aren’t available.
• Avoid touching your eyes, nose and mouth as much as possible.
• Clean and disinfect surfaces that may be contaminated with the flu virus.
• Stay home for at least 24 hours after your fever has subsided.
• Get your annual flu shot each fall.
• Take flu antiviral drugs (like Tamiflu) if your doctor prescribes them.

A bout of the flu can last for a few days or a few weeks. Often, people who’ve gotten a flu shot will get over their infection a little faster compared to people who weren’t vaccinated, per Harvard Health Publishing.

Flu symptoms like a fever, chills or body aches often come on suddenly, peak and then slowly subside. (The average flu incubation period, or the period of time between exposure to the virus and the appearance of symptoms, is two days.)

“The second through the fourth days are usually the worst,” says Nikhil Bhayani, MD, an infectious disease physician with Texas Health Resources in Bedford, Texas.

You’ll know you’re nearing the end of the flu when your fever has gone down (without taking any medicine) and your body isn’t as achy. “That usually means the virus is controlled,” Dr. Bhayani says.

But your coughing, runny nose or fatigue might stick around for a few more days. You may even get flu dizziness that lasts for days to weeks, depending on the cause.

If you have the flu, you’re most contagious during the first three days you’re sick, per the CDC. But you’re likely contagious for a day before symptoms start and several more after.

Let’s break that down: An infected person can spread the flu a day before their symptoms actually start. So, if the average incubation period is two days, you might be contagious a day or so after coming into contact with someone who’s sick or some other exposure to the flu virus.

You’re most contagious during that peak symptom period, around days two through four, according to the Cleveland Clinic. But you can keep on spreading the virus until your symptoms clear up altogether. That usually takes about five to seven days, per Harvard Health Publishing, but it could take longer.

In other words, typically you’re no longer contagious with the flu once your symptoms have completely gone away, Dr. Bhayani says.

Taking an antiviral medication like Tamiflu can shorten the duration of your flu symptoms, and in turn cut down on the amount of time you’re contagious by a day or two, he adds.

But even if you’re experiencing mild symptoms, you can still spread the virus.

Keep in mind that taking over-the-counter meds that simply lower your fever (like ibuprofen or acetaminophen) won’t actually help you get over the flu faster or make you less contagious. They just make you more comfortable while you’re dealing with flu symptoms, per the Cleveland Clinic.

Most people don’t need to seek medical attention for the flu, especially if you’re otherwise healthy. But it’s a good idea to reach out to your doctor if you or your loved one is at high risk for flu complications like pneumonia, according to the Mayo Clinic.

That includes people under 12 or over 65, pregnant people, people with chronic medical conditions, people with a weakened immune system, people with a BMI over 40 and people living in a nursing home or other care facility. In that case, your doctor might prescribe an antiviral medication like Tamiflu to help keep your symptoms in check.

Seek emergency medical care if you or your loved one are experiencing concerning symptoms, such as:

• Trouble breathing
• Chest pain
• Dizziness or confusion
• Bluish lips or face
• Severe weakness
• Symptoms that get worse after getting better
• Fever over 104 degrees Fahrenheit

Here’s some more important info on the flu and how to stay healthy.