What is flu (influenza)?

Influenza (flu) is an infection from a virus. It can cause a fever, body aches, a headache, and a cough. It is contagious and usually lasts about a week or two. Flu symptoms are usually worse than a cold and last longer. The flu usually doesn't cause vomiting or diarrhea in adults.

Most flu outbreaks happen in late fall and winter. Because symptoms may not start for a couple of days, you may pass the flu to someone before you know you have it.

The symptoms of influenza (flu) appear suddenly. They often include:

• Fever.
  • Fever is usually continuous, but it may come and go.
  • Fever may be lower in older adults than in children and younger adults.
• Body aches and muscle pain (often severe).
• A headache.
• Pain when you move your eyes.
• Fatigue, a general feeling of sickness, and loss of appetite.
• A dry cough, a runny nose, and a dry or sore throat.

Symptoms are usually worse for the first few days. But it can take up to a few weeks to get completely better.

It usually takes 1 to 4 days to get flu symptoms after you've been around someone with the virus. Some people can have the flu virus without having any symptoms.

The flu usually doesn't cause symptoms in the stomach or intestines, such as vomiting and diarrhea.

Your doctor will ask you about your symptoms and will examine you. This usually gives the doctor enough information to know if you have the flu, especially if many cases of a similar illness have occurred in the area and the local health department reports a flu outbreak.

In some cases, the doctor may take a sample of fluid from your nose or throat. This may be done to confirm the flu. Or it can be done to find out what type of flu virus you have. Some tests give a result right away. Others take a few days.

A rapid flu test gives results quickly. Because rapid flu tests aren't completely accurate, your doctor may diagnose you with the flu even if the test doesn't confirm it.

Most people can treat flu symptoms at home. Home treatment includes resting, drinking plenty of fluids, and taking medicine to lower your fever. But some people need to go to the hospital for treatment. They may have severe symptoms or get pneumonia. Or the flu infection may make an existing health problem worse.

If you think you have the flu, your doctor may be able to give you an antiviral medicine that can make the symptoms milder and lessen the length of time you have the flu.

These antiviral medicines are often given to people who are very sick with the flu or to those who are likely to have problems caused by the flu. But they may also be used for a person who has been sick with the flu for less than 48 hours.

Give your child acetaminophen (Tylenol) or ibuprofen (Advil, Motrin) for fever, pain, or fussiness. Do not use ibuprofen if your child is less than 6 months old unless the doctor gave you instructions to use it. Be safe with medicines. Read and follow all instructions on the label. Do not give aspirin to anyone younger than 20. It has been linked to Reye syndrome, a serious illness. Don't give cough and cold medicines to children under 6.