Disease & Vaccine A–Z

Diseases beginning with F

U.S.-focused summaries with current official guidance links. For a diagnosis, personal vaccine schedule, pregnancy advice, or urgent symptoms, speak with a qualified clinician.

Flu (Influenza)

Annual vaccine

Disease

A contagious respiratory illness caused by influenza viruses.

Symptoms

Often sudden fever or chills, cough, sore throat, runny nose, muscle aches, headache, and fatigue.

Typical duration

Most uncomplicated cases improve in several days to under two weeks.

How serious is it?

Can cause pneumonia, worsen chronic conditions, lead to hospitalization, and cause death.

Treatment & management

Rest and fluids help mild illness. Prescription antivirals work best when started early and are especially important for higher-risk or severe cases.

Vaccine: who and when?

Current U.S. seasonal products include Fluzone, Fluarix, FluLaval, Flucelvax, FluMist, Flublok, and age-specific products such as Fluad and high-dose Fluzone. CDC recommends vaccination each season for everyone age 6 months and older, with product choice and one- versus two-dose childhood schedules based on age and history.

Check the current CDC guidance for Flu (Influenza) →

Cost and access: Patient cost varies by insurance, provider, location, and eligibility. Many recommended vaccines are covered with no out-of-pocket cost under qualifying plans, and eligible children may receive vaccines through the Vaccines for Children program. CDC price lists are purchasing benchmarks—not guaranteed patient prices. CDC price and program context.

Last reviewed against official U.S. sources: September 5, 2026. This page provides general education, not medical advice.