Influenza (Flu) | CDC
Influenza (flu) is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and lungs. Learn about flu, including symptoms, prevention methods, and treatment options.
Influenza - Wikipedia
Influenza A virus and influenza B virus circulate in humans and cause seasonal epidemics, and influenza C virus causes a mild infection, primarily in children. Influenza D virus can infect humans …
Influenza (flu) - Symptoms and causes - Mayo Clinic
Dec 19, 2025 · Flu, also called influenza, is an infection of the nose, throat and lungs, which are part of the respiratory system. The flu is caused by a virus. Influenza viruses are different from the "stomach …
About Influenza | Influenza (Flu) | CDC
Feb 26, 2026 · Flu can cause mild to severe illness. Some people are at higher risk for more serious flu illness. Getting a flu vaccine has been shown to reduce the risk of flu and serious flu complications. …
Flu (Influenza): Causes, Symptoms, Types & Treatment
Oct 11, 2022 · What is the flu (influenza)? The flu is an illness you get from the influenza virus. It causes symptoms like head and body aches, sore throat, fever and respiratory symptoms, which can be …
Influenza (seasonal) - World Health Organization (WHO)
Feb 28, 2025 · Seasonal influenza (the flu) is an acute respiratory infection caused by influenza viruses. It is common in all parts of the world. Most people recover without treatment. Influenza spreads …
Influenza (flu) - Diagnosis and treatment - Mayo Clinic
Dec 19, 2025 · Learn more about how to get your flu shot at Mayo Clinic. To diagnose the flu, also called influenza, your healthcare professional does a physical exam, looks for symptoms of flu and possibly …
Influenza | Definition, Symptoms, Treatment, & Prevention | Britannica
May 26, 2026 · Influenza is an acute viral infection of the upper or lower respiratory tract, marked by fever, chills, and a generalized feeling of malaise. Seasonal influenza (the flu) is a major global …
Influenza A vs. Influenza B - Cleveland Clinic Health Essentials
Jan 22, 2025 · Influenza A and influenza B are the main strains of flu virus. Type A causes more cases, more severe illness and infects many species. Type B only infects humans.
Flu (Influenza) - Harvard Health
Apr 16, 2026 · Influenza (the flu) is a respiratory infection. It is caused by the influenza virus. Influenza typically is spread by air or by direct contact from one person to another. Influenza virus is very …