Got the Flu? Here’s How Long You’re Contagious

The flu (influenza) is a respiratory illness caused by influenza viruses. These viruses are very contagious, which means they can spread easily between people. That’s why about 1 in 9 people in the U.S. get sick with the flu every year. 

The flu can sometimes be mild. But it can also cause more serious illness, hospitalization, and even death. It’s important to take steps to limit the spread of influenza viruses when you’re sick with the flu. This helps protect people who are at risk for serious flu illness. Here’s how long you’re contagious with the flu and what you should do when you’re sick.

How does the flu spread?

Flu viruses spread from person to person, either through the air or by contact with contaminated surfaces. 

Most experts believe that when someone with the flu talks, coughs, or sneezes, it releases droplets into the air. These droplets can be inhaled by people nearby, especially those less than 6 feet away. 

Less often, the droplets infect people by landing on surfaces. You can get the flu if you touch a contaminated surface and then touch your own nose or mouth. 

Once inside your body, the flu virus attacks your nose, throat, and lungs. This leads to flu symptoms like sore throat, fatigue, and fever.

How contagious is the flu?

Influenza viruses are very contagious.

The virus multiplies quickly in your nose and throat and can spread before you start to feel sick. A person with the flu can still be contagious, even without a fever.

Experts estimate that every person who is sick with the flu spreads it to one or two other people.

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When are you contagious with the flu?

You’re most contagious with the flu during the first 3 days of your illness. But you can spread the flu even before you start feeling sick. You can also spread the flu while your symptoms are getting better. 

In general, you’re more contagious at the peak of your illness when you have symptoms like fever, cough, congestion, and body aches. As your immune system fights off the virus, those symptoms begin to improve. When that happens, you release less of the virus, which makes you less contagious. 

You’re no longer contagious with the flu once your symptoms are gone, and you feel back to normal. That’s the sign that your immune system has cleared the virus from your body. 

Most of the time, people with the flu are contagious for about a week after getting sick. But some people stay contagious for longer, especially children and people who are immunocompromised. Their flu symptoms also linger longer. That’s because it takes their immune systems longer to fight off the flu virus. 

How do you know if you have the flu?

Flu symptoms can be similar to those of other viral illnesses, like COVID-19 and the common cold. Flu symptoms include:

• Fever

• Cough

• Runny nose

• Sore throat

• Body aches

• Fatigue

• Chills

• Headache

Flu symptoms tend to start suddenly, while common cold symptoms come on gradually. 

Often the best way to know if you have the flu is to be aware of what is spreading in your community. If others around you have the flu, chances are high that the flu is what’s causing your symptoms.

Can you get tested for the flu? 

Yes, a flu test can tell you if you have the flu. But most people with the flu don’t need a flu test during flu season unless treatment with antiviral medications is needed.

Antiviral medications can lower your risk of severe flu illness. Not everyone needs to take these medications when they’re sick with the flu. 

These medications work best when started within 48 hours of your first symptoms. If you have flu-like symptoms, it’s a good idea to contact your healthcare team. They can help you determine if you need a flu test or should start antiviral medications. 

Rapid flu tests are available in health clinics, urgent care centers, and some pharmacies. At-home tests for flu and COVID are also available. But it can take several days to get your results back. 

How can you protect yourself and others during flu season?

A yearly flu shot is the best way to protect yourself and others during flu season. 

You can still get sick with the flu even after getting vaccinated. But you’re less likely to develop severe illness if you do get sick. And most people only experience mild symptoms if they have a breakthrough infection. 

A flu shot also lowers your chances of spreading influenza viruses to others. This can keep vulnerable loved ones safe. Everyone in your household should get vaccinated against the flu if you live with:

• An infant younger than 6 months old

• An adult older than 65 years old

• An infant or toddler born prematurely

• Someone with a weakened immune system

• Someone with a history of a stem cell or organ transplant

• Someone receiving treatment for cancer

• Someone with a history of heart or lung problems

Here are more ways to protect yourself, your loved ones, and your community from the flu:

• Wear a mask in crowded areas when there’s high flu activity in your area.

• Clean your hands regularly with soap or an alcohol-based sanitizer.

• Avoid touching your face, especially when in public.

• Keep your distance from others who are sick.

• Cover your mouth and nose with a tissue when you cough or sneeze.

• Stay home if you have flu symptoms.

How long should you stay home when you have the flu?

Experts recommend staying home while you have the flu until both of the following are true:

• You have been fever-free for at least 24 hours (without fever-reducing medications).

• Your symptoms have been getting better for at least 24 hours. 

For most people, this takes about 4 to 5 days. Staying home will stop the spread of the flu and protect others from getting sick.

What to do if someone in your household is sick

If someone in your household has the flu, take steps to keep the rest of your family (or roommates) healthy. Here’s how to slow the spread at home:

• Create a “sick room.” Have the person who’s ill use a separate bedroom and bathroom, if possible. If you can’t create a sick room, consider wearing masks indoors.

• Don’t share personal items. Give the sick person their own personal items to use, like drinking glasses, towels, and pillows. If possible, clean these items before sharing with others in the household. 

• Keep indoor air clean. Open windows or use an air purifier to make it harder for the flu to spread.

• Keep surfaces clean. Regularly clean surfaces that may have flu germs on them. This includes doorknobs, counters, bathrooms, electronics, and bedding, towels, or dishes used by the sick person.

• Call their healthcare team. Contact their healthcare team to see if they need a flu test or antiviral medication.

Need more information? Check out this guide from the CDC for detailed instructions on how to care for someone with the flu.

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Written by:

Sarah Gupta, MD

Sarah Gupta, MD, is a licensed physician with a special interest in mental health, sex and gender, eating disorders, and the human microbiome. She is currently board certified by the American Board of Psychiatry and Neurology.

Edited by:

Patricia Pinto-Garcia, MD, MPH

Patricia Pinto-Garcia, MD, MPH, is a medical editor at GoodRx. She is a licensed, board-certified pediatrician with more than a decade of experience in academic medicine.

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