Influenza (flu) is a contagious disease present in the United States yearly usually between October and May. It is caused by influenza viruses that are spread mainly by coughing, sneezing and close contact. Flu can affect anyone and strikes suddenly lasting several days. Symptoms vary by age, but include fever/chills, sore throat, muscle aches, fatigue, cough, headache, and runny or stuffy nose.
Influenza infections can lead to pneumonia and infections in the blood. Children can have diarrhea and seizures. Medical conditions such as heart or lung disease can be made worse by influenza.
Flu is more dangerous for some people. Infants and young children, people 65 years of age and older, pregnant women, and people with certain health conditions or a weakened immune system are at greatest risk.
Thousands of people die each year from influenza and many more are hospitalized. Receiving a flu vaccine can keep you from getting the flu, make flu less severe if you do get it, and keep you from spreading it to your family and other people.
There is no live virus in flu shots. They cannot cause the flu.
Flu vaccine cannot prevent infections caused by a virus not covered by the vaccine or illnesses that look like flu but are not. It takes about two weeks for protection to develop after vaccination and protection last through the influenza season.