Flu Fact Sheet

What is the flu?

The flu (short for "influenza") is an illness caused by viruses. Flu viruses can infect a person's nose, throat, and lungs.

When is flu season?

Flu season usually begins in December and lasts through March in New England.

How is seasonal flu different from pandemic flu?

A pandemic occurs when an illness becomes widespread because it is easily passed from one human to another. In the past 100 years, there have been three flu pandemics. A pandemic virus strain is likely to affect more people because humans have not previously been exposed to this particular virus.  For more information, see the Cambridge Public Health Department's fact sheet on pandemic flu.  

Is flu dangerous?

Flu can be a serious illness. Every year, an average of 23,000 people living in the United States die from flu-related complications.

Anyone can get the flu, but some people can become very sick. People who are at highest risk for becoming very sick from the flu include:

• Adults age 50 or older
• Children under 5 years
• Pregnant women
• People with chronic illnesses
• People with weak immune systems

Most people recover from the flu within 1 to 2 weeks.

How is flu spread?

Flu viruses live in the nose and throat of an infected person. When an infected person coughs, sneezes, or talks, flu viruses are spread into the air. People nearby can breathe in the viruses and become sick. An infected person is can spread the flu a day before symptoms appear and can remain contagious for up to a week later. A child with flu can be contagious longer than a week.

What are flu symptoms?

Flu symptoms appear 1 to 5 days after exposure, and may include:

• Fever (102° to 104°), lasting 3 to 5 days
• Chills
• Headaches
• Sore throat
• Severe muscle aches
• Tiredness, which can be extreme and can last two weeks or more
• Dry cough
• Runny or stuffy nose

Serious complications from flu include dehydration, pneumonia, bronchitis, and sinus and ear infections. Flu infection can also make chronic health problems worse.

Who should get vaccinated?

Anyone who wants to reduce their risk of getting the flu should get vaccinated. However, during flu seasons when vaccine supplies are limited or delayed, priority should be given to people at high risk for becoming very sick from the flu and their caregivers.

Based on 2010 CDC guidelines, priority populations are: 

• All children age 6 months through 5 years.
• Adults age 50 or older.
• Anyone with a chronic health condition—such as asthma, diabetes, heart disease or a compromised immune system—that puts them at higher risk of medical complications from influenza. 
• Pregnant women.
• Children receiving long-term aspirin therapy.
• Residents of nursing homes and long-term care facilities.
• People who are obese (body mass index greater than 40)
• Health care workers and first responders who could give the flu to people at high risk for severe illness.
• Caregivers of children under age 5 and adults age 50 or older.
• American Indians and Alaska Natives.

If you get a flu shot can you still get the flu?

The flu shot is 70% to 90% effective in preventing flu or at least reducing symptoms. It usually takes two weeks after the shot to develop maximum protection, which then gradually wears off.  The flu shot does not cause the flu.

What should I do if I get the flu?

For more information about how to care for someone with the flu and when to seek medical attention, see the Massachusetts Department of Public Health's Caring for People at Home booklet, which is available in many languages. 

How can I prevent the flu?

These simple actions can protect you from getting the flu and help stop the spread of germs.

• Get a flu shot every year. A flu shot is the best way to protect yourself against seasonal flu. You should get a flu shot every fall because the viruses that cause the flu change every year.
• Get a pneumonia shot if you are age 65 or older, or if you have a medical condition like diabetes, asthma, or heart disease.
• Wash your hands often. Use soap and rub your hands together for 20 seconds. Alcohol-based gels and wipes also work well.
• Avoid touching your eyes, nose, or mouth.
• Wipe down door handles, water faucets, phones, and other household items that are frequently touched by family members.
• Avoid close contact with sick people.
• Stay home when you are sick to prevent others from catching your illness.
• Cough or sneeze into the inside of your arm, not your hands.
• Dispose of tissues properly, and wash your hands after using tissues.

Other good habits, such as getting plenty of sleep, engaging in physical activity, managing stress, drinking water, and eating good food, will help you stay healthy during the winter and all year.

Sources: Cambridge Public Health Department (Public Health Nursing Program), Massachusetts Department of Public Health, and Boston Public Health Commission.

Last revised on September 14, 2010