A man

Seasonal influenza, or the flu, comes on suddenly, causing symptoms such as fever, body aches, headache, and tiredness. You also can lose your appetite and have a dry cough and a sore or dry throat.

The flu is not the same as the common cold. Flu symptoms are usually more severe, and you will often miss more work or school than you would with a cold. The flu usually occurs during the late fall and winter. It is caused by a virus.

Most people get better without problems. Sometimes the flu leads to a bacterial infection, such as an ear infection or sinus infection. Good home treatment may help prevent these infections.

Some people may have more serious problems, such as pneumonia. Young children, older adults, and people with long-term health problems are more likely to have serious problems from the flu.

What causes the flu?

The flu is usually caused by influenza viruses type A or B. These viruses cause the outbreaks that occur each year.

Type B usually results in a milder flu than type A. These viruses constantly change, producing what are called subtypes or strains that are different from the original virus but still have some of its traits. Flu strains can change from year to year.

What are the symptoms?

The time from when you are exposed to the flu virus until you have symptoms is 1 to 4 days.

Symptoms come on suddenly and include:

  • A fever.
  • Cough.
  • Shaking chills.
  • Body aches.
  • Headache.
  • Feeling very tired.

Symptoms of the flu usually last for 3 to 4 days. After this you may have a dry cough, a runny nose, and a sore or scratchy throat for another week or so.

Some people, especially people who smoke, have a dry cough for weeks.

How is it diagnosed?

Your doctor usually can diagnose the flu by asking you questions about your symptoms.

Routine testing of people who have flu symptoms is usually not necessary.

Rarely, the specific flu virus you have may be identified through a blood test or a nasal or throat swab.

How is it treated?

Home treatment is usually all that you need. Expect the illness to go away on its own in about 7 to 10 days.

In the meantime, you can take steps to feel better:

  • Get extra rest. Bed rest can help you feel better. It will also help you avoid spreading the virus to others.
  • Drink plenty of extra fluids to replace those lost from fever. Extra fluids also ease a scratchy throat and keep nasal mucus thin. Water, fruit juice, soup, and hot tea with lemon are all good choices.
  • Take acetaminophen (Tylenol) or ibuprofen (Advil, Motrin) to lower your fever. You may also sponge your body with lukewarm water to reduce fever. Do not use cold water or ice. Lowering the fever will not make your symptoms go away faster, but it may make you more comfortable.
  • To relieve body aches and headache, take an over-the-counter pain reliever. Be safe with medicines. Read and follow all instructions on the label. No one younger than 20 should take aspirin. It has been linked to Reye syndrome, a serious illness.
  • If you give medicine to your child, follow the package instructions carefully. For your baby, follow what your doctor has told you about the amount of medicine to give. Talk to your child's doctor before switching back and forth between doses of acetaminophen and ibuprofen. There's a chance your child will get too much medicine.
  • To help clear a stuffy nose, breathe moist air from a hot shower or a sink full of hot water.
  • Use cough drops or plain, hard candy to help ease coughing.
  • Elevate your head at night with an extra pillow if coughing keeps you awake.
  • Avoid smoking and secondhand smoke.

Your doctor may suggest an antiviral medicine (oseltamivir or zanamivir) to reduce the length and severity of your flu. It may reduce the length of your illness by only a couple of days. To work best, it should be started within 2 days of your first symptoms.

How well antiviral medicines work can vary from year to year as flu viruses change. Ask your doctor which one is best for you.

Can the flu be prevented?

You can help prevent the flu by getting a flu vaccine each year, as soon as it's available.

Everyone age 6 months and older should get a flu vaccine each year. Children younger than 9 years of age may need two doses, depending on when they started getting this yearly vaccine.

Getting the flu vaccine is especially important for people who are at high risk for getting other health problems from the flu and for those who are in close contact with people who are at high risk.

The risk is higher for:

  • Children younger than 4 years of age.
  • Adults ages 65 and older.
  • People who have health problems like asthma, chronic heart or lung disorders, or a weak immune system.
  • Women who will be pregnant during the flu season.
  • People who live in nursing homes or long-term care centers.

Instead of a flu shot, you may choose to get a nasal spray vaccine.

It is a live-virus vaccine, which means the vaccine can cause symptoms similar to a cold, but it does not cause the flu. It is recommended only for healthy children and adults between the ages of 2 and 49.

It is not recommended for pregnant women. It should not be given to close contacts of people who have very weak immune systems, such as those who have had a recent bone marrow transplant, to avoid their spreading the virus after being vaccinated.

Most, but not all, types of flu vaccine contain a small amount of egg.

To help prevent the spread of all viruses, including the flu, wash your hands often and cover your coughs and sneezes. Also try to avoid people who are sick.