What is flu?

Influenza, also called the flu, is an infection caused by a virus. The flu affects your whole body, especially your air passages, and causes symptoms that are similar to cold symptoms. Flu symptoms tend to be worse than cold symptoms, but it can sometimes be hard to tell the difference between the flu and a cold unless you get a test.

Infection with the flu virus sometimes leads to other infections, such as ear, sinus, and chest infections. Pneumonia can also occur as a result of the flu. It can be caused by the flu virus itself or by bacteria infecting lung tissues that have been damaged by the virus. Older adults; people whose immune systems are weak; and people with chronic medical problems, such as heart or lung disease or diabetes, are at risk for more severe symptoms or problems. This is why it’s important to try to prevent flu by getting flu shots every year.

What is the cause?

Flu is caused by a virus. When you have the flu, the virus is in your mucus and saliva and can spread to others when you cough or sneeze. People can also get the flu if they touch something with the flu virus on it (like cups, doorknobs, and hands) and then touch their mouth, nose, or eyes.

Outbreaks of flu occur every year, usually in late fall and winter.

What are the symptoms?

Flu tends to start suddenly. You may feel fine one hour and feel sick the next. Flu symptoms may be different from person to person. Some of the common symptoms include:

• Chills, sweating, and fever
• Cough
• Runny or stuffy nose
• Headache
• Muscle or body aches
• Sore throat
• Tiredness

Flu symptoms usually last 3 to 7 days. You may start feeling better after the first 2 days or so.

How is it diagnosed?

Your healthcare provider will ask about your symptoms and may examine you. The diagnosis is usually based on your symptoms. There are lab tests for flu, but in most cases there is no need to do a test, especially when many others in your community are sick with the flu.

How is it treated?

Usually you can treat your symptoms at home.

• Get plenty of rest.
• Drink a lot of clear liquids. Water, broth, juice, electrolyte solutions, and noncaffeinated drinks are best. When you have a high fever, your body needs more liquid because you lose more water in your breath and from your skin. Having enough fluids also helps the mucus in your sinuses and lungs stay thin and easy to clear from the body. When the mucus is thin, it is less likely to cause a sinus or chest infection.
• Consider taking acetaminophen or ibuprofen to relieve headaches and muscle aches and to lower a fever. Read the label and take as directed. Unless recommended by your healthcare provider, you should not take these medicines for more than 10 days.
  • Nonsteroidal anti-inflammatory medicines (NSAIDs), such as ibuprofen, naproxen, and aspirin, may cause stomach bleeding and other problems. These risks increase with age.
  • Acetaminophen may cause liver damage or other problems. Unless recommended by your provider, don’t take more than 3000 milligrams (mg) in 24 hours. To make sure you don’t take too much, check other medicines you take to see if they also contain acetaminophen. Ask your provider if you need to avoid drinking alcohol while taking this medicine.
• If your nose or sinuses get congested, a decongestant medicine may help you feel better. Taking a decongestant may help prevent ear or sinus infections.
• Cough medicine or cough drops may temporarily help control a cough.

Antiviral medicine is medicine your healthcare provider can prescribe that may make flu symptoms less severe. It may also help you feel better a little sooner. Examples of this medicine are zanamivir (Relenza) and oseltamivir (Tamiflu). The medicine can be taken as a tablet or nasal spray. It helps only if you start taking it within the first 2 days of illness. Usually it is taken for only a few days. Even if you are taking antiviral medicine, you can pass the flu virus to other people. It is still important to wash your hands often and cover your mouth and nose when you cough or sneeze.

Your healthcare provider may prescribe antiviral medicine if you aren’t sick yet but have been exposed to the flu and have not had the flu vaccine.

Talk to your healthcare provider if you have symptoms of the flu and:

• You have heart disease, asthma, chronic bronchitis, kidney disease, diabetes, or another chronic medical problem.
• Your immune system does not work normally (for example, because you are taking steroid medicine for a medical problem).
• Your symptoms get more severe, you have a painful cough, you are coughing up mucus, or you are having trouble breathing. These symptoms can be signs of pneumonia.

Ask your healthcare provider:

• How and when you will hear your test results
• How long it will take to recover from this illness
• What activities you should avoid, and when you can return to your normal activities
• How to take care of yourself at home
• What symptoms or problems you should watch for and what to do if you have them

Make sure you know when you should come back for a checkup.

How can I help prevent flu?

The flu vaccine is the best way to help prevent the flu. If you do get the flu, the vaccine may help keep you from getting really sick. The flu vaccine is recommended for adults and children 6 months and older. It’s especially important for those with a chronic illness.

The flu vaccine can be given as a shot or as a nasal spray.

• The shot contains killed virus and is safe for everyone age 6 months and older.
• The nasal spray contains a weakened, live virus and can be given only to healthy children over age 2 and healthy adults who are not pregnant and younger than age 50. Pregnant women, children under 2 years, people 50 or older, or people who have weakened immune systems, asthma, or some other medical conditions cannot take the nasal spray. If you are thinking about getting the nasal spray, ask your provider if it is recommended for you.

You should get a new flu shot every year because the vaccine wears off over time and because it is changed each year to protect against the current year’s most likely flu strains. It’s best to get the new vaccine as soon as it’s available each year, before the start of flu season. However, if the vaccine is still available, it can be helpful to get it anytime during the flu season. Flu season usually starts in October and can last through May.

Flu seasons can vary from region to region. If you are at high risk for infection and plan to travel to an area where you might be exposed to the flu, make sure you have an up-to-date flu shot before you go on your trip.

Other things you can do to help avoid getting the flu are:

• Wash your hands often with soap and water. Wash for 20 seconds (long enough to sing the whole “Happy Birthday” song) or use an alcohol-based hand cleaner.
• Avoid touching your eyes, nose, or mouth when you are out in public.
• Stay at least 6 feet away from people who are sick, if you can.
• Try to take good care of yourself: Get plenty of sleep, be physically active, manage your stress, drink plenty of fluids, and eat healthy food. Stop smoking.
• Keep surfaces clean–especially bedside tables, surfaces in the bathroom, and toys for children. Some viruses and bacteria can live 2 hours or more on surfaces like cafeteria tables, doorknobs, and desks. Wipe them down with a household disinfectant according to directions on the label.

If you are sick, you can help protect others if you:

• Don’t go to work or school. Avoid contact with other people except to get medical care.
• Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it, and then wash your hands. If you don’t have a tissue, cough or sneeze into your upper sleeve instead of your hands.
• Clean your hands often with soap and water or an alcohol-based hand cleaner, especially after using tissues or coughing or sneezing into your hands.