What is Influenza (Also Called Flu)?

The flu is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times can lead to death. The best way to prevent the flu is by getting a flu vaccination each year.

Every year in the United States, on average:

• 5% to 20% of the population gets the flu;
• more than 200,000 people are hospitalized from flu complications, and;
• about 36,000 people die from flu.

Some people, such as older people, young children, and people with certain health conditions, are at high risk for serious flu complications.

Symptoms of Flu

Symptoms of flu include:

fever (usually high) headache extreme tiredness dry cough sore throat

runny or stuffy nose muscle aches Stomach symptoms, such as nausea, vomiting, and diarrhea, also can occur but are more common in children than adults

Complications of 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.

How Flu Spreads

Flu viruses spread mainly from person to person through coughing or sneezing of people with influenza. Sometimes people may become infected by touching something with flu viruses on it and then touching their mouth or nose. Most healthy adults may be able to infect others beginning 1 day before symptoms develop and up to 5 days after becoming sick. That means that 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.

Preventing the Flu: Get Vaccinated

The single best way to prevent the flu is to get a flu vaccination each year. There are two types of vaccines:

• The "flu shot" – an inactivated vaccine (containing killed virus) that is given with a needle. The flu shot is approved for use in people 6 months of age and older, including healthy people and people with chronic medical conditions.
• The nasal-spray flu vaccine – a vaccine made with live, weakened flu viruses that do not cause the flu (sometimes called LAIV for “Live Attenuated Influenza Vaccine”). LAIV is approved for use in healthy people 5 years to 49 years of age who are not pregnant.