Influenza (Seasonal Flu)

Cause

The flu is usually caused by the influenza viruses types A and B. Each type includes several subtypes.

The influenza virus changes often. There are different subtypes of the flu virus every year. So having the flu caused by one type doesn't give you immunity to other types.

The virus is spread from person to person through:

• Direct contact, such as shaking hands.
• Small droplets that form when a person sneezes or coughs.
• Contact with objects, such as doorknobs, phones, or keyboards, that may have droplets from an infected person.

What Increases Your Risk

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.
• People who are pregnant.
• People who have chronic obstructive pulmonary disease (COPD), other lung diseases, or heart failure.
• People who have a medical condition, such as cancer, or who are using a medicine that impairs the immune system.

Prevention

You can help prevent the flu by staying up-to-date on the flu vaccine. Everyone older than 6 months can get it every year. It is especially important for people at high risk for problems from the flu to stay up-to-date. Talk to your doctor about what is best for you. You can also go to the U.S. Centers for Disease Control and Prevention (CDC) website at cdc.gov/flu/prevention to get more information.

People at higher risk of problems from the flu include:

• Young children.
• Adults age 65 and older.
• Adults and children who have long-term health problems or a weak immune system.
• People who are pregnant.

The vaccine is also important for health care workers and anyone who lives or works with someone at higher risk of problems from the flu.

You can also help avoid getting the flu by staying away from people who are sick, washing your hands often, keeping your hands away from your face, eating a balanced diet, exercising regularly, and not smoking.

Symptoms

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

• A fever. Not everyone will have a fever.
• Chills.
• A cough.
• A sore throat.
• A runny or stuffy nose.
• Muscle or body aches.
• A headache.
• Fatigue.

Symptoms are usually worse for the first few days. It can take up to a few weeks to feel 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. These symptoms are more common in children than adults.

What Happens

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 can be serious in older adults, people who have other health conditions, and in people who are pregnant.
• Bronchiolitis. This is an inflammation of the small airways. It affects infants and can cause a serious lower respiratory infection.
• 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.
• Worsening symptoms from chronic obstructive pulmonary disease (COPD) or other lung conditions.
• Inflammation of the heart muscle, the sac around the heart, or other muscles in the body.

When to Call a Doctor

Call 911 or other emergency services if:

• You have severe trouble breathing, or you feel very short of breath.
• You have a seizure.
• You have pain or pressure in your chest.

Contact your doctor if:

• You have trouble breathing or are wheezing.
• You have a fever with a stiff neck or a severe headache.
• You feel very sleepy, dizzy, or confused.
• You have an extremely high fever.
• Your fever lasts longer than 3 days.
• Your child is 3 months of age or younger and has a fever of 100.4 °F (38 °C) or higher.
• You are coughing up yellow, green, rust-colored, or bloody mucus.
• Your cough lasts more than 7 to 10 days after other symptoms are gone.
• New pain develops or pain narrows to one area, such as an ear, the throat, the chest, or the sinuses.
• Symptoms don't go away, even with home treatment.
• Symptoms become more severe or frequent.

Watchful waiting

In most healthy people, the flu will go away in 5 to 7 days, although feeling tired can last much longer. You may feel very sick, but home treatment is usually all that is needed. If it's flu season, you may just want to treat your symptoms at home. Watch closely for symptoms of a bacterial infection, such as nasal drainage that changes from clear to colored after 5 to 7 days and symptoms that return or get worse.

Early treatment with an antiviral medicine may reduce the severity of influenza and may prevent more serious problems. It's best to start these medicines right away. Babies, older adults, and people who have chronic health problems are more likely to have problems from the flu, and they may need to see a doctor for treatment. But not all antiviral medicines work against all strains of the flu. Talk to your doctor if you think you may need an antiviral medicine.

Contact your doctor if you think your symptoms are caused by something other than the flu.

Exams and Tests

Your doctor will ask about your symptoms and medical history and do a physical exam. This usually gives the doctor enough information to know if you have the flu, especially if the local health department reports many cases of the flu in the area.

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. Rapid test results can vary depending on the type of rapid test used and on the type of influenza viruses that are being reported in your area. Your doctor may diagnose you with the flu even if the test doesn't confirm it.

Treatment Overview

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 condition worse.

If you think you have the flu, your doctor may be able to give you an antiviral medicine in the first 2 days that can make the symptoms milder and shorten 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.

Self-Care

If you have the flu, it may take a few weeks to feel better. In the meantime, you can take steps to help your symptoms.

• Get plenty of rest.
• To prevent dehydration, drink plenty of fluids. Choose water and other clear liquids until you feel better. If you have kidney, heart, or liver disease and have to limit fluids, talk with your doctor before you increase the amount of fluids you drink.
• Try a sponge bath with lukewarm water. Don't use cold water, ice, or rubbing alcohol.
• Try an over-the-counter medicine to help relieve your symptoms. Acetaminophen (Tylenol), ibuprofen (Advil, Motrin), or naproxen (Aleve) may help relieve fever, headache, and muscle aches. Be safe with medicines. Read and follow all instructions on the label. Do not give aspirin to children or teens. It has been linked to Reye syndrome, a rare but serious illness.
• Take steps to ease your coughing.
  • Suck on cough drops or plain, hard candy.
  • Try an over-the-counter cough and cold medicine. Read and follow all instructions on the label. Don't give them to children younger than 6, because they don't work for children that age and can even be harmful. For children 6 and older, always follow all the instructions carefully. Make sure you know how much medicine to give and how long to use it. And use the dosing device if one is included.
  • Prop up your head at night with an extra pillow. This may help you rest if coughing keeps you awake.
• If the skin around your nose and lips becomes sore, put some petroleum jelly (such as Vaseline) on the area. Using disposable tissues that contain lotion also may help.
• Don’t smoke, vape, or use other tobacco or nicotine products. These things can make the flu worse. If you need help quitting, talk to your doctor about quit programs and medicines. These can increase your chances of quitting for good.