Influenza (General Information)

(Last reviewed 12/16/2011)

For information on the novel swine-origin influenza H3N2, see our Influenza Surveillance page or the CDC Swine Flu website.

What is Influenza (Flu)?

Influenza, or flu, is a respiratory illness caused by influenza viruses. Symptoms of influenza include fever (often high), runny or stuffy nose, cough, sore throat, headache, tiredness, and muscle aches. Children may sometimes also have nausea, vomiting and diarrhea. Some people can have a severe illness with influenza. They may have pneumonia, ear infections, dehydration, and worsening of medical problems such as asthma, heart conditions, and diabetes. People with chronic medical conditions, the elderly, pregnant women, and children under 2 years of age are more likely to be admitted to a hospital for influenza. More than 200,000 people are hospitalized each year in the United States due to flu and between about 3,000 to 49,000 people die.

How does it spread?

Flu is spread by droplets produced by coughing and sneezing. It usually spreads from person to person but occasionally objects such as a doorknob can become contaminated with the virus and serve as a source of infection also.

What can I do to prevent the spread of influenza?

Vaccination is the best prevention method available.

People who are sick should stay home and avoid close contact with others. Good health habits such as washing your hands often, covering your mouth and nose with a tissue when coughing or sneezing, and avoiding touching your eyes, mouth, or nose can prevent you and/or others from becoming ill. Antiviral medications are available that can prevent or lessen the severity of influenza infection; however, these medications should only be used for those who are at higher risk of severe illness.