How Contagious Is the Flu? Odds of Getting & Spreading

The flu is extremely contagious. The influenza virus, which causes the flu, spreads easily—especially in fall and winter. When someone with the flu coughs, sneezes, or talks, they release tiny droplets into the air. These virus-containing droplets can enter your nose, eyes, or mouth, infecting your lungs and throat. You can also acquire the flu by touching surfaces contaminated with the virus and touching your face.

The flu affects 9-41 million people annually in the United States, resulting in around 100,000-710,000 hospitalizations and 4,900- 51,000 deaths. Knowing how contagious the flu is, how people get it, and how it’s spread can help protect you and others during the flu season.

When someone with the flu coughs, sneezes, or talks, they release tiny respiratory droplets into the air. These droplets can land in someone else’s eyes, nose, or mouth, allowing the virus to infect them.

Close proximity to someone with the flu (within a yard or meter) makes you more likely to catch it. Children spread the infection easily, likely because they aren’t as aware of hand and respiratory hygiene.

The flu virus can also survive on surfaces like doorknobs, countertops, and phones for 24-48 hours. You can develop the flu if you touch these surfaces and then touch your face, especially your nose, mouth, or eyes.

You’re most contagious during the first three days of having symptoms. However, you can spread the flu even before you know you’re sick, starting the day before symptoms begin.

Flu symptoms are similar to a cold but usually more intense. They come on quickly and include:

• Body aches
• Chills
• Cough
• Fever, 100-104 degrees Fahrenheit (37.8-40 degrees Celcius) in adults or 100 degrees Fahrenheit (37.8 degrees Celsius) in children
• Runny or stuffy nose
• Sore throat
• Upset stomach

You can still spread the flu for 5-7 days after symptoms began, even if you feel better. Young children, older adults, and people with weakened immune systems may be contagious for even longer (10 days or more).

Age is a significant factor in your risk of developing or becoming very sick from the flu. Young children under 5 (especially babies less than 6 months old) and adults over 65 are at a higher risk for contracting the flu because their immune systems aren’t as strong.

Pregnant people and those with weakened immune systems are also more at risk of getting the flu. This includes people with chronic (long-term) health conditions like asthma, diabetes, heart disease, human immunodeficiency virus (HIV), or severe obesity.

People receiving chemotherapy or taking immunosuppressants (anti-rejection drugs) after an organ transplant also have weaker immune systems, making it harder to fight viruses like the flu.

Being close to someone with the flu increases your chances of getting it. The flu spreads quickly in crowded places like schools, offices, cruise ships, and public transportation, where it’s easier to come into contact with infected people or the surfaces their droplets land on. Healthcare workers are at even higher risk because they are often around more people with illnesses.

The flu vaccine is the best way to prevent getting sick and spreading the flu. Since the flu virus changes yearly, everyone older than 6 months should get an annual flu vaccine before flu season. In the U.S., flu season typically occurs in the fall and winter and peaks between December and February.

If you get the flu or have a positive flu test, stay home and avoid close contact with others until you’ve been fever-free for 24 hours without using fever-reducing medicine. Cover your mouth and nose when you cough or sneeze, and wash your hands often to stop the virus from spreading to others. You should also avoid touching your face, especially with unwashed hands.

Because the flu virus can live on surfaces for 24-48 hours, cleaning and disinfecting regularly is important. Cleaner air can reduce the risk of exposure to viruses. You can improve air quality by bringing in fresh air from the outside, using air purifiers indoors, or spending time outdoors.

If you have the flu and must be in close contact with others, wearing a mask can protect you and those around you. Masks can help reduce the spread of flu viruses from someone who has the flu or prevent infectious particles from reaching those who don’t.

For most healthy people, the flu goes away on its own within a week. Treatment for mild symptoms includes taking medicine like Tylenol (acetaminophen) to lower fever, drinking lots of fluids, resting, and staying home from school or work until you’ve been fever-free for at least 24 hours.

You should visit your healthcare provider if you have a fever longer than three days, symptoms aren’t improving, have signs of dehydration, or are at high risk for severe flu illness.

Antiviral medicines can reduce the flu’s length and make symptoms less severe. Healthcare providers recommend antivirals if you’re in a high-risk group, haven’t had the flu shot, were vaccinated less than 14 days ago, or live or work in places with an outbreak.

If you feel you need antiviral medication, reach out to a healthcare provider within the first 48 hours after flu exposure or symptoms begin. These medicines work best when taken within this time frame.

Common antivirals include:

• Tamiflu (oseltamivir): This comes in a pill or liquid and is for people 14 days or older.
• Relenza (zanamivir): This is an inhaled powder for people 7 years and older. It works best when taken within 36 hours and is not recommended for those with asthma.
• Rapivab (peramivir): This is given intravenously (IV) by a provider and is suitable for people 6 months or older.
• Xofluza (baloxavir marboxil): This is a single-dose pill for children ages 5-12 with no chronic health conditions and all people 12 and older. It’s not recommended for people who are pregnant or breastfeeding.

Go to urgent care if you or your loved one has persistent symptoms that aren’t improving, like a high fever, diarrhea, or vomiting. Someone with severe body aches, extreme tiredness, or symptoms that improve and then worsen should be seen immediately.

Seek emergency care if you or someone you know has:

• Blue or gray lips or face
• Chest pain or pressure
• Confusion
• Difficulty breathing
• Fainting
• Fever above 104 degrees Fahrenheit (40 degrees Celsius) in adults or any fever in children under 12 weeks (100.4 degrees Fahrenheit, 38 degrees Celsius)
• Severe dehydration, signs of which may include producing little or no urine
• Severe dizziness or weakness

The flu is a highly contagious virus that spreads through droplets in the air when someone coughs or sneezes or when you touch your face after touching an infected surface. The flu is most contagious during the first few days someone has symptoms. However, it can spread even before someone feels sick and up to 10 days after symptoms develop.

Young children, older adults, pregnant people, and anyone with a weak immune system have the highest risk of flu infection. To reduce the risk of getting or spreading the flu, get a flu vaccine yearly, wash your hands often, clean surfaces regularly, cover your mouth when coughing or sneezing, and stay home if you’re sick.

If you have severe symptoms or are at high risk for complications, see a healthcare provider quickly to discuss antiviral treatment.