Influenza, the illness most people just call the flu, is a viral infection of the breathing passages. It spreads easily from person to person and can involve the nose, throat and lungs. It makes millions of Americans ill in a typical year.
How it shows up, and who is more at risk
Symptoms often arrive all at once. They may include a fever or a feverish feeling, chills, coughing, a sore throat, congestion, sore muscles, a headache and deep tiredness. Most people get well, but the illness can be serious or even fatal, especially for adults over 65, young children, newborns and people with certain long-term conditions such as heart disease or asthma.
The two types that usually circulate in people and drive the yearly wave are influenza A and influenza B.
The strongest protection, plus daily habits
The strongest protection is a flu vaccine every year. Everyday habits also help keep germs from spreading: cover a cough, and wash your hands often. Lather with soap under the tap for a full 20 seconds, including before you eat.
If you do get sick
Anyone with a mild case should remain at home and keep away from other people, except to get medical care. If symptoms appear and you are in a higher-risk group, feel very sick, or are worried, call a clinician. Antiviral drugs can ease the illness and shorten it, and they usually work best if started within two days of getting sick. They can also help prevent dangerous complications.