How long is the flu contagious?

The flu is contagious for about 24 hours after your fever breaks. Here’s what you need to know about avoiding the spread of the flu and when you’re contagious.

Published: January 24, 2025

Estimated reading time: 5 minutes

Influenza, or flu, is an upper respiratory infection caused by a virus. It affects the nose, lungs and throat. This influenza is not the same as a stomach flu, which may cause vomiting, nausea and diarrhea. 

Most people recover on their own from influenza. Sometimes, the flu and its complications can be deadly. There is a flu vaccination, which can reduce your risk of getting the flu and the severity of flu symptoms. 

You are contagious for a period of time around your illness. Understanding when flu is contagious is important to stop the spread of seasonal flu. 

Understanding the flu virus

Flu is contagious via small droplets from your respiratory system that are expelled when you speak, cough or sneeze. These respiratory droplets can land in someone’s mouth, nose or eyes. In some cases, it spreads when someone touches an infected surface then touches their own nose or eyes. 

Common flu symptoms include:

• Fever, although not everyone with flu has a fever
• Cough
• Chills and sweating
• Muscle aches
• Fatigue
• Sore throat
• Runny nose

Symptoms come on suddenly with flu. Common cold symptoms build more gradually over time.

Contagious period with the flu

Flu takes one to four days to incubate in your system after you come into contact with the virus. You have the potential to spread flu before symptom appear. You are contagious for about three to seven days after symptoms appear. An infected person can spread flu even if they never develop symptoms severe enough to notice they are sick.

“Overall, you can be contagious or were contagious the day before you noticed any symptoms. You still can spread the flu for about a week after you started feeling sick or as long as you have symptoms,” said Rachel N. Alexander, APRN, nurse practitioner with Norton eCare. After symptoms decrease, the virus may continue to shed. Those with a weakened immune system may continue to shed flu virus for longer than an otherwise healthy person. 

The severity of your case of flu, your individual immune response and your flu vaccination status affect how long the flu is contagious. While the flu vaccination is not a guarantee you will not get the flu, it affects the severity of your symptoms and may help control overall flu spread.

Preventing flu spread

• Importance of staying home while contagious
• Proper hygiene practices (hand-washing, covering coughs, disinfecting surfaces)
• Use of masks in public or around vulnerable populations

If you develop symptoms of the flu, stay home and avoid contact with others. Wipe down surfaces in your home with antiviral wipes, wash your hands often and refrain from close contact with others in your home. If you are at higher risk for developing complications for the flu, seek immediate medical attention. 

Flu complications

Some people are at a higher risk of developing more severe symptoms of the flu. These groups include:

• Adults ages 65 and older
• Children under 5
• Pregnant women
• People with chronic health conditions
• People with weakened immune systems
• People with a body mass index of 40 or higher (Class III obesity)

If you develop these symptoms seek immediate medical attention:

• Difficulty breathing
• Persistent pain or pressure in the chest or abdomen
• Persistent dizziness, confusion or inability to wake up
• Seizures
• Not urinating (peeing)
• Severe muscle pain
• Fever or cough that improves then returns or worsens
• Worsening of chronic medical conditions

When can I resume normal activity after the flu?

Most flu symptoms go away in four to seven days for otherwise healthy adults, but you still may be contagious. You may go back to light exercise when you feel like it, but listen to your body and rest when you need to. The Centers for Disease Control and Prevention advises staying home for at least 24 hours after your fever goes away without the help of ibuprofen (Motril or Advil) or acetaminophen (Tylenol).

A flu vaccination is the best way to prevent spreading seasonal flu. The vaccine has been shown to reduce illness, doctor’s visits, time off work or school due to flu, and lower the risk of serious complications. 

Besides vaccination, everyday steps you can take to prevent seasonal flu spread include:

• Avoid contact with sick people and stay away from others if you are sick.
• Cover your nose and mouth with a tissue if you cough or sneeze, then throw the tissue away. If you cough or sneeze into your hand, wash your hands immediately.
• Wash hands often with soap and water. If those are not available, use an alcohol-based hand sanitizer.
• Avoid touching your mouth, eyes and nose. 
• Clean and disinfect surfaces that may be infected with flu virus.

There are many ways to protect yourself, your loved ones and your community from the flu. Getting a flu shot is the first step.