Contagious Period for Influenza (Flu)

What Is the Incubation Period for the Flu?

The contagious period for influenza, also known as the flu, usually begins about 1 day before symptoms appear and continues for about 5 to 7 days after illness begins. People are generally most contagious during the first 3 days of illness. Young children and people with weakened immune systems may remain contagious longer. Some people can have influenza without symptoms and may still spread the virus. The incubation period is the time between infection and the start of symptoms. For influenza, it is typically 1 to 4 days, with symptoms often beginning around 2 days after infection.

To avoid spreading the flu to others, here are some recommendations:

• Stay home: Stay home and away from others until, for at least 24 hours, your symptoms are improving overall and you have not had a fever without using fever-reducing medicine. Because you may still be able to spread the virus after returning to normal activities, take added precautions for the next 5 days, such as improving airflow, practicing good hygiene, keeping distance from others, or wearing a well-fitting mask.
• Practice good hygiene: Cover your mouth and nose with a tissue or your elbow when you cough or sneeze to prevent droplets from spreading.
• Avoid close contact: Try to avoid close contact with people who are sick, and if you are sick, avoid close contact with others. This includes hugging, kissing, shaking hands, and sharing utensils or personal items.
• Wear a mask: A well-fitting mask can help reduce the spread of influenza, especially when you are sick or recovering, when respiratory viruses are circulating widely, or when you are around someone at higher risk of severe illness. The mask should fit closely and cover both your nose and mouth.
• Improve air quality: Open windows or use air purifiers to improve ventilation in indoor spaces. Good air circulation can help reduce the concentration of respiratory droplets in the air.
• Practice hand hygiene: Wash your hands frequently with soap and water for at least 20 seconds, especially after coughing, sneezing, blowing your nose, or touching surfaces that may be contaminated with flu viruses. If soap and water are not available, use hand sanitizer with at least 60% alcohol.
• Get vaccinated: Annual influenza vaccination is the best way to reduce the risk of flu and its potentially serious complications. It is recommended for most people 6 months of age and older, with rare exceptions.
• Ask about antiviral treatment: Contact a healthcare professional promptly if you are at higher risk of flu complications, are very sick, or your illness is worsening. Prescription antiviral medicines work best when started within 2 days after symptoms begin, but starting later can still help some people with severe illness or higher-risk conditions.

A healthcare professional can provide advice about influenza, the incubation and contagious periods, prevention, and treatment based on your circumstances. Get medical care right away if you have any of these:

• Trouble breathing
• Chest pain
• Confusion
• Severe weakness
• Signs of dehydration
• Symptoms that improve, then come back or get worse