Flu is a respiratory infection caused by a number of viruses. The viruses pass through the air and enter your body through your nose or mouth. Between 5% and 20% of people in the U.S. get the flu each year. Even healthy people can get very sick from the flu and spread it to others.
Anyone can get the flu (even healthy people), and serious problems related to the flu can happen at any age, but some people are at high risk of developing serious flu-related complications if they get sick. This includes people 65 years and older, people of any age with certain chronic medical conditions (such as asthma, diabetes, or heart disease), pregnant women, and young children. During flu season we offer flu treatment clinical trials which provide a no-cost alternative to the limited treatments that are currently available. Select one of locations below to find an enrolling flu treatment clinical trial near you. Use the form on the page to make a same-day appointment.
Most people who get influenza will recover in several days to less than two weeks, but some people will develop complications as a result of the flu.
Complications of flu can include bacterial pneumonia, ear infections, sinus infections, dehydration, and worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes.
Most experts believe that flu viruses spread mainly by droplets made when people with flu cough, sneeze or talk. These droplets can land in the mouths or noses of people who are nearby. Less often, a person might also get flu by touching a surface or object that has flu virus on it and then touching their own mouth, eyes or possibly their nose.
You may be able to pass on the flu to someone else before you know you are sick, as well as while you are sick. Most healthy adults may be able to infect others beginning 1 day before symptoms develop and up to 5 to 7 days after becoming sick. Some people, especially young children and people with weakened immune systems, might be able to infect others for an even longer time.
The time from when a person is exposed to the flu virus to when symptoms begin is about 1 to 4 days, with an average of about 2 days. It is very difficult to distinguish the flu from other viral or bacterial causes of respiratory illnesses on the basis of symptoms alone. There are tests available to diagnose flu. The main way to keep from getting the flu is to get a yearly flu vaccine. Good hygiene, including hand washing, can also help.
Symptoms of the flu come on suddenly and are worse than those of the common cold: