Influenza (Flu)



The flu is caused by different strains of the influenza virus. The strain that is most common changes from year to year. The virus is spread from person to person when someone who is ill sneezes or coughs. This releases small amounts of virus in the air for a short time. Others nearby can then inhale the virus in the air. The virus can also live on surfaces for a time. A person can also get sick from touching a surface where the virus is, then touching their mouth or nose.

Risk Factors

Things that raise the risk of getting the flu are:

  • Living or working in crowded areas—such as nursing homes, schools, daycare centers, and the military
  • Having a physical or mental disability

Some people have a higher risk for severe flu, or problems from the flu. This includes:

  • Children less than 5 years of age
  • Adults who are at least 50 years of age
Other things that raise the risk of severe flu are:

  • Asthma
  • Diabetes
  • Diseases of the heart, kidneys, liver, blood, or nervous system
  • A weak immune system
  • Pregnancy
  • Obesity



Symptoms often start quickly. They may be:

  • High fever and chills
  • Headache and severe muscle aches
  • Severe tiredness
  • Lack of hunger or nausea, vomiting, and diarrhea
  • Cough, sneezing, and runny or stuffy nose
  • Watery eyes, or red eyes from conjunctivitis
  • Sore throat
  • Swollen lumps (lymph nodes) in the neck


The doctor will ask about symptoms and past health. A physical exam may be done. Diagnosis is often based on symptoms.

The doctor may take samples from the nose or throat for testing, but it is rare.



Most can clear the virus on their own. The flu usually lasts seven to 10 days. A cough or feeling tired may last longer. People with severe symptoms or problems may be treated in the hospital.

Treatment can help ease discomfort until the flu passes. Options include:

  • Home care—such as rest and drinking plenty of fluids
  • Symptom treatment with over the counter medicine, such as:
    • Acetaminophen or ibuprofen—to reduce pain and fever
    • Cough remedies
    • Antihistamines— to ease a runny nose, or itchy and watery eyes
    • Decongestants—often used to ease stuffiness, but may not be the most effective choice
  • Antiviral medicines—for severe symptoms or people at risk for them

Hospital care may include fluids and breathing support.


To reduce the risk of getting the flu:

  • Get a yearly flu vaccine. Everyone 6 months of age and older should think about getting a flu vaccine. It is safe and often helpful for those with chronic health conditions and people who are pregnant. Talk to the doctor if there are any questions.
  • Wash hands often.
  • Stay away from people who are sick.
  • Do not share drinks or personal items.
  • Keep surfaces clean with disinfectants.

Antiviral medicines may be advised for certain people.

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

Edits to original content made by Denver Health.