When is flu infectious

More information is available: Diagnosing Flu. There are influenza antiviral drugs that can be used to treat flu illness. To receive weekly email updates about Seasonal Flu, enter your email address:.

Skip directly to site content Skip directly to page options Skip directly to A-Z link. Influenza Flu. Section Navigation. Facebook Twitter LinkedIn Syndicate. Key Facts About Influenza Flu. Minus Related Pages. What is Influenza Flu? Flu Symptoms Influenza flu can cause mild to severe illness, and at times can lead to death.

On This Page. What is Influenza also called Flu? How Flu Spreads. Who is most likely to be infected with influenza? An infected person can spread the influenza virus even before feeling sick. An adult can spread the virus from about 1 day before to 5 days after symptoms start.

Young children may be able to spread the virus for a longer period of time. Influenza symptoms can include fever, headache, muscle pain, runny nose, sore throat, extreme tiredness and cough.

Children may also experience nausea, vomiting or diarrhea. Although infections from other viruses may have similar symptoms, those due to the influenza virus tend to be worse. Symptoms can begin about 1 to 4 days, or an average of 2 days, after a person is first exposed to the influenza virus. Fever and other symptoms can usually last up to 7 to 10 days, but the cough and weakness may last 1 to 2 weeks longer.

If you get sick with influenza, home treatment can help ease symptoms. Follow the self-care advice below:. But children and adults at high risk may develop complications that may include:. Pneumonia is one of the most serious complications. For older adults and people with a chronic illness, pneumonia can be deadly. The flu vaccine can reduce your risk of the flu and its severity and lower the risk of having serious illness from the flu and needing to stay in the hospital.

Flu vaccination is especially important this season because the flu and coronavirus disease COVID cause similar symptoms. Preventing the flu and reducing the severity of flu illness and hospitalizations could also lessen the number of people needing to stay in the hospital. This year's seasonal flu vaccine provides protection from the four influenza viruses that are expected to be the most common during the year's flu season.

This year, the vaccine will be available as an injection and as a nasal spray. Avoid crowds. The flu spreads easily wherever people gather — in child care centers, schools, office buildings, auditoriums and public transportation.

By avoiding crowds during peak flu season, you reduce your chances of infection. Also avoid anyone who is sick. And if you're sick, stay home for at least 24 hours after your fever is gone so that you lessen your chance of infecting others. Your local health department and the CDC may suggest other precautions to reduce your risk of COVID or the flu if you haven't been fully vaccinated. For example, you may need to practice social distancing physical distancing and stay at least 6 feet 2 meters from others outside your household.

You may also need to wear a cloth face mask when indoors with people outside your household and when outdoors in crowded areas. If you're fully vaccinated and are in an area with a high number of new COVID cases in the last week, the CDC also recommends wearing a mask indoors in public and outdoors in crowded areas or when you're in close contact with unvaccinated people.

Mayo Clinic does not endorse companies or products. Advertising revenue supports our not-for-profit mission. This content does not have an English version. This content does not have an Arabic version. Overview Influenza is a viral infection that attacks your respiratory system — your nose, throat and lungs. The flu spreads through tiny wet drops produced when a person coughs, sneezes, or talks. A person can get the flu by breathing in these wet drops, or by touching items and surfaces covered with these drops and then touching their mouth, nose, or eyes.

People who have the flu may spread it to others about 1 day before getting sick to 5 -7 days after. Children and people with weak immune systems can spread the flu virus for a longer period of time. However, people are most contagious during the first three days of illness.

The usual signs and symptoms of the flu are cough, sore throat, runny or stuffy nose, body aches, headache, chills, and feeling very tired. Most people also have a fever. Others may vomit and have diarrhea.