Flu (Influenza)

What is flu?

Flu is a respiratory illness that spreads from person to person. It can cause mild to severe illness. Serious outcomes of flu can result in hospitalization or death.

Some people, such as older people, young children, pregnant women, and people with certain health conditions, are at high risk of serious flu complications.


Flu is caused by a virus that is spread from person to person. It causes seasonal epidemics each year.


Flu symptoms can occur suddenly. You might have the flu if you have some or all of these symptoms:

  • fever (not everyone with flu will have a fever)
  • cough
  • body aches
  • sore throat
  • runny or stuffy nose
  • headache
  • chills
  • fatigue
  • sometimes diarrhea and vomiting


Most people who get flu will recover in a few days to less than two weeks. But some people will develop complications (such as pneumonia) as a result of flu, some of which can be life-threatening and result in death.

Moderate complications of flu include:

  • sinus infections
  • ear infections

Possible serious complications triggered by flu can include:

  • lung infection (pneumonia)
  • inflammation of the heart, brain, or muscle
  • organ failure (for example, respiratory and kidney failure)
  • sepsis, which can be deadly

Flu also can make chronic medical problems worse. For example:

  • If you have asthma, flu may trigger asthma attacks.
  • If you have chronic heart disease, flu may make your condition worse.

When to Seek Medical Care

These are the emergency warning signs of flu sickness.

In children:

  • fast breathing or trouble breathing
  • bluish lips or face
  • ribs pulling in with each breath
  • chest pain
  • severe muscle pain (child refuses to walk)
  • dehydration (no urine for 8 hours, dry mouth, no tears when crying)
  • not alert or interacting when awake
  • seizures
  • fever above 104°F
  • in children less than 12 weeks old, any fever
  • fever or cough that improve but then return or worsen
  • worsening of chronic medical conditions

These are not all of the possible emergency warning signs of flu. Contact your doctor about any other symptoms that are severe or concerning.

If you have the emergency warning signs of flu sickness, you should obtain medical care right away.

In adults:

  • difficulty breathing or shortness of breath
  • persistent pain or pressure in the chest or abdomen
  • persistent dizziness, confusion, inability to arouse
  • seizures
  • not urinating
  • severe muscle pain
  • severe weakness or unsteadiness
  • fever or cough that improve but then return or worsen
  • worsening of chronic medical conditions

High-risk Group:

If you have symptoms of flu and are in a high-risk group, or are very sick or worried about your illness, contact your doctor.

High-risk groups include:

  • young children
  • children with neurologic conditions
  • pregnant women
  • adults 65 years and older
  • anyone with these conditions:
    • asthma
    • heart disease
    • stroke
    • diabetes
    • HIV/AIDS
    • cancer


Your doctor might prescribe antivirals drugs for flu. These drugs can make you better faster and may also prevent serious complications.

If you are in a high-risk group and develop flu symptoms, you need to contact your doctor when you first notice flu symptoms. Remind them about your high-risk status for flu. See Treatment – Antiviral Drugs for more information.

Antiviral drugs need to be taken within 2 days of your first flu symptoms.

Antibiotics Won’t Help

When you have flu, antibiotics will not help you feel better.  Antibiotics won’t help you, and their side effects could cause harm.

Side effects of antibiotics can range from minor issues, like a rash, to very serious health problems, such as

If you use over-the-counter medicines, take them as directed. Remember, over-the-counter medicines may provide temporary relief of symptoms, but they will not cure your illness.

Antibiotics won’t help if you have flu.

Over-the Counter Medicine and Children

Be careful about giving over-the-counter medicines to children. Not all over-the-counter medicines are recommended for children of certain ages.

Pain relievers:

  • Children younger than 6 months: only give acetaminophen.
  • Children 6 months or older: acetaminophen or ibuprofen can be given.

Cough and cold medicines:

  • Children younger than 4 years old: do not use unless specifically directed by a doctor. Use of over-the-counter cough and cold medicines in young children can result in serious and potentially life-threatening side effects.
  • Children 4 years or older: discuss with your child’s doctor if over-the-counter cough and cold medicines are safe to give to your child for temporary symptom relief.

Be sure to ask your doctor or pharmacist about the right dosage of over-the-counter medicines for your child’s age and size. Also, tell your child’s doctor and pharmacist about all prescription and over-the-counter medicines they are taking.

Never give aspirin to children younger than 19 years old. Aspirin can cause Reye syndrome, a rare but very serious illness that harms the liver and brain.


The best way to prevent flu is by getting vaccinated with the flu vaccine each year.

Other ways to avoid flu:

  • Try to avoid contact with sick people.
  • If you are sick, limit contact with others as much as possible to keep from infecting them.
  • Cover your nose and mouth with a tissue when you cough or sneeze. After using a tissue,
    • throw it in the trash and
    • wash your hands.
  • Wash your hands often with soap and water. If soap and water are not available, use an alcohol-based hand rub.
  • Avoid touching your eyes, nose, and mouth. Germs spread this way.
  • Clean and disinfect surfaces and objects that may be contaminated with germs like flu.

When Can You Return to Work or School?

CDC recommends that you stay at home for at least 24 hours after your fever is gone except to get medical care or other necessities.

Your fever should be gone without the use of fever reducing medicines.