Please note: This information was current at the time of publication but now may be out of date. This handout provides a general overview and may not apply to everyone. 

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Am Fam Physician. 2010;82(9):1097-1098

See related article on influenza

What is influenza?

Influenza, also called the flu, is a viral infection of the nose, throat, and lungs. It is often confused with other illnesses, especially the common cold. The flu is more severe than a cold, usually comes on suddenly, and is caused by a different virus. In 2009, a new strain of flu called H1N1 or “swine flu” made many people sick.

What are some symptoms of the flu?

The most common symptoms are chills, fever, headache, sore throat, cough, runny or stuffy nose, muscle aches, weakness, and fatigue. Some people may have vomiting and diarrhea.

Most people who have the flu get better within a few days to a couple of weeks. In some people, the flu causes other problems, such as dehydration, ear infections, sinus infections, and pneumonia. Serious complications from the flu can happen at any age, but they are more likely in children younger than two years and in adults 65 years and older. The flu can also make certain health problems worse, such as asthma, diabetes, and heart problems.

How is it spread?

Flu viruses are spread through body fluids from an infected person, such as through coughs or sneezes. They are also spread by shaking hands or touching objects that have been handled by someone with the flu, such as doorknobs, grocery cart handles, money, elevator buttons, remote controls, telephones, and computer keyboards.

Flu symptoms usually start about two days after the virus enters the body. This means you can spread the virus to others even before you know you are sick. People with the flu are contagious for up to 24 hours after their fever ends. Some people can be infected with the flu virus but have no symptoms. These people can still spread the virus to others.

What can I do to prevent the flu?

  • Get a flu shot. This year's shot contains the 2009 H1N1 virus plus two other flu viruses. Everyone six months and older should get a flu shot this year.

  • Stay away from people who are sick.

  • Wash your hands often. Use soap and hot water, and wash for at least 15 seconds. Carry alcohol-based hand sanitizer with you for times when you're away from a sink.

  • Do not touch your eyes, nose, or mouth. If you have touched something that has been handled by someone who is sick, your hands may have the flu virus on them.

  • Take care of yourself. Get plenty of sleep and exercise, drink a lot of water, and eat a healthy diet, including at least five servings of fruits and vegetables each day.

What should I do if I get the flu?

If you have symptoms of the flu, do not go to work or school. Stay home and get plenty of rest, drink a lot of water, and do not smoke or drink alcohol. Most people who get the flu do not need to see a doctor. Very young children, older adults, and people with certain medical conditions are more likely to get very sick from the flu. These people may need to see a doctor.

Go to the emergency room right away if you have any of the following symptoms:

In children

  • Fast breathing or trouble breathing

  • Bluish skin color

  • Trouble drinking enough fluids

  • Trouble waking up

  • Irritability

  • Fever with a rash

  • Symptoms that get better, but then return with fever and worse cough

In adults

  • Trouble breathing

  • Chest or stomach pain

  • Dizziness

  • Confusion

  • Severe vomiting

  • Symptoms that get better, but then return with fever and worse cough

Do I need medicine?

Over-the-counter medicine, such as acetaminophen (one brand: Tylenol) or ibuprofen (one brand: Motrin), can help with fever and muscle aches. Children and teenagers should not take aspirin because it can cause a rare but serious liver disease.

Most people who get the flu do not need prescription medicine. Because the flu is caused by a virus, antibiotics do not help. Medicines called antivirals may help you get better faster and prevent complications. Antivirals are usually prescribed for people who are very sick and need to be hospitalized, and for people who are likely to get serious complications from the flu. Your doctor will decide whether you need antiviral medicines.

Where can I get more information?

Your doctor

AAFP's Patient Education Resource

Centers for Disease Control and Prevention

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