What is flu (influenza)?

Influenza (flu) is an infection in the respiratory tract. It is caused by the influenza virus. There are different strains of the flu virus from year to year. Unlike the common cold, the flu comes on suddenly, and the symptoms, such as a cough, congestion, fever, chills, fatigue, aches, and pains, are more severe. These symptoms may last for a few weeks. Although the flu can make you feel very sick, it usually does not cause serious health problems.

Home treatment is usually all you need for flu symptoms. But your doctor may prescribe antiviral medicine to prevent other health problems, such as pneumonia, from developing. Teens who have a long-term health condition, such as asthma, are more at risk for having pneumonia or other health problems.

Flu symptoms may include fever, body aches, a headache, a dry cough, and a sore or dry throat. You'll probably feel tired and less hungry than usual. The symptoms are usually worse for the first few days. But it can take up to a few weeks to get completely better.

Most people can treat flu symptoms at home with rest, medicines, or other treatment. Your doctor may give you medicine that can make the symptoms milder. But some people need treatment in the hospital. They may have severe symptoms or get pneumonia. Or the flu infection may make an existing health problem worse.

Your doctor will ask you about your symptoms and will examine you. This usually gives the doctor enough information to find out if you have the flu. Sometimes the doctor will do a test to check for the flu.

Get lots of rest and drink plenty of fluids. Breathe moist air to help a stuffy nose. For coughing, drink fluids to soothe your throat and suck on cough drops or hard candy. Elevate your head at night if coughing wakes you up. Take over-the-counter medicines for pain or cough if needed.

Anyone exposed to the flu virus can get the flu. These flu viruses spread easily among people in groups. For example, people in nursing homes, hospitals, shelters, schools, and day care can easily be exposed to the flu virus. Working, visiting, or living in any of these areas puts you at more risk of getting the flu.

The risk of having severe symptoms and complications is higher for:

• Children younger than 2 years of age.
• Adults age 65 and older.
• Pregnant women.
• People who have chronic obstructive pulmonary disease (COPD), other lung diseases, or heart failure.
• People who have a medical condition (such as AIDS) or who are using a medicine that impairs the immune system.

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.

Although most cases of influenza (flu) get better without causing other problems, complications sometimes develop.

Possible problems from the flu include:

• Pneumonia, which is an infection of the lungs. It rarely causes death in young, healthy people. But it can often be life-threatening in older adults, people who have other diseases, and pregnant women.
• Bronchiolitis. This is an inflammation of the small air passages. It affects infants and is the leading cause of serious lower respiratory illness.
• Sinusitis. This means the mucous membranes that line the inside of the nose and facial sinuses become infected and inflamed.
• Croup. Croup is a swelling or blockage in the windpipe. It causes hoarseness, a barking cough, a high-pitched sound when breathing in, and trouble breathing.
• Chronic obstructive pulmonary disease (COPD) symptoms may get worse.
• Inflammation of the heart muscle, the sac around the heart, or other muscles.

The flu is usually caused by the influenza viruses types A and B. There are different subtypes, or strains, of the flu virus every year.