Flu (Influenza)

Influenza (flu) is a contagious viral infection that can cause mild to severe symptoms and life-threatening complications, including death, even in healthy children and adults.

Influenza viruses spread mainly from one individual to another through coughing or sneezing. Less often, they can also spread through touching a contaminated surface and then touching the mouth, eyes, or nose. Individuals can pass flu on to others even before their own symptoms start and for a week or more after symptoms begin.

Burden

While the numbers vary, in the US, millions of individuals get sick, hundreds of thousands are hospitalized, and tens of thousands die from flu and related complications each year. Flu also affects employers and businesses and costs an estimated $11.2 billion in direct and indirect costs in the US annually. During the 2019-2020 flu season, flu vaccination prevented approximately 7.5 million flu illnesses, 105,000 hospitalizations, and 6,300 deaths.

Symptoms

Flu is not just a common cold. It usually comes on suddenly, and people with flu may have some or all of the following symptoms (think F.A.C.T.S.):

Fever
Aches (muscle, body, and headaches)
Chills
Tiredness (fatigue)
Sudden onset
Cough, runny or stuffy nose, and/or sore throat
Vomiting and diarrhea (more common in children than adults)

Prevention

The best way to prevent flu is to receive an influenza vaccination every year. The Centers for Disease Control and Prevention (CDC) recommends that everyone age 6 months and older get vaccinated annually. Flu vaccination is especially important this year to help protect individuals and prevent additional strain on an already overburdened US healthcare system. The best time to get vaccinated is in the early fall, before influenza viruses begin spreading in your community. However, vaccination throughout the flu season is still beneficial.

Flu vaccines are updated annually to protect against the influenza viruses research indicates are most likely to circulate during the upcoming season. Flu vaccines can vary in how well they work, but even in cases when flu vaccination does not prevent infection completely, it can reduce the severity and duration of disease and prevent serious complications. For more than 50 years, hundreds of millions of individuals in the US have safely received seasonal flu vaccines.

View ACIP Recommendations for the Prevention and Control of Seasonal Influenza during the 2021-2022 Influenza Season

Treatment

Annual flu vaccination is the best way to prevent flu. Antiviral drugs are not a substitute for annual flu vaccination; however, prescription antiviral medications serve as an additional line of defense. CDC recommends that all individuals who are hospitalized, severely ill, or at high risk for developing serious flu-related complications should be treated with antiviral drugs immediately if flu is suspected.

Treatment of flu with antiviral drugs can reduce influenza symptoms, shorten the duration of illness by one to two days, and prevent serious complications, like pneumonia. Antivirals work best when taken within 48 hours of getting sick, but may still be beneficial when given later in the course of illness.

Healthcare professionals may treat patients based on their clinical judgment and knowledge about the level of local flu activity. For additional information, see CDC Influenza Antiviral Medications: Summary for Clinicians.

Updated September 2021

Source: Centers for Disease Control and Prevention