Flu (short for "influenza") is a very contagious disease of the body's respiratory (breathing) system. Flu symptoms include sudden fever, cough, muscle aches, headache and general weakness. Flu usually also causes runny nose and sore throat. These symptoms can range from very mild to very severe.

Is flu dangerous?

It can be. Most people are sick for only a few days. Some people, however, may develop pneumonia. Every year in the U.S., flu causes thousands of hospital admissions and deaths, mostly among the elderly, pregnant women and people with chronic medical problems and weakened immune systems.

How is flu spread?

The viruses that cause flu live in the nose and throat and are sprayed into the air when an infected person sneezes, coughs or talks. People nearby can then breathe in the virus. Flu symptoms usually start 1 to 3 days after a person breathes in the virus. People with the flu can spread it from 1 day before symptoms appear to 1 week after.

When does flu occur?

In New England, flu season usually begins in December and lasts through March. A flu-like illness that happens in the summer is usually not the flu. However, travelers may get the flu at any time of the year.

How is flu treated?

Bed rest, plenty of fluids and non-aspirin pain relievers help most people feel better. Remember children and teens with the flu should never take aspirin. Prescription drugs, called antiviral agents, can be used to prevent or treat the flu. These drugs can cause side effects in some people. You should talk to your doctor or nurse about taking these drugs.

Can I protect myself from getting the flu?

YES. A flu shot can prevent the flu. Flu viruses change often, so last year's vaccine will not protect you this year. You must get a flu shot every year. The flu shot will begin to protect you about 2 weeks after you get it. It is very important that people who are at risk (see below), and the people who live or work with them, get a flu shot every year.

When should I get a flu shot?

Flu shots are usually given before flu season starts, beginning in September or as soon as flu vaccine is available. Sometimes flu vaccine is delayed. When this happens, people who are most at risk of getting very sick or dying from the flu should get the flu shot first. If you are 65 years old or older, or you have one of the conditions listed on the next page, you should call your doctor or board of health to get the flu shot as soon as vaccine is available. If you are a healthy person younger than 65 years old who wants to avoid getting the flu, you should wait until November or December to get the flu shot. You can get a flu shot anytime during flu season. Because flu season lasts until March, December or even later is not too late to get the shot.