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Summary
What is the flu?
The flu, also called influenza, is a respiratory infection caused by viruses. Each year, millions of Americans get sick with the flu. Sometimes it causes mild illness. But it can also be serious or even deadly, especially for people over 65, newborn babies, and people with certain chronic illnesses.
What causes the flu?
The flu is caused by flu viruses that spread from person to person. When someone with the flu coughs, sneezes, or talks, they spray tiny droplets. These droplets can land in the mouths or noses of people who are nearby. Less often, a person may get flu by touching a surface or object that has flu virus on it and then touching their own mouth, nose, or possibly their eyes.
What are the symptoms of the flu?
Symptoms of the flu come on suddenly and may include:
- Fever or feeling feverish/chills
- Cough
- Sore throat
- Runny or stuffy nose
- Muscle or body aches
- Headaches
- Fatigue (tiredness)
Some people may also have vomiting and diarrhea. This is more common in children.
Sometimes people have trouble figuring out whether they have a cold or the flu. There are differences between them:
Signs and Symptoms | Cold | Flu |
---|---|---|
Start of symptoms | Slowly | Suddenly |
Fever | Rarely | Usually |
Aches | Sometimes (slight) | Usually |
Fatigue, weakness | Sometimes | Usually |
Headache | Rarely | Common |
Stuffy nose, sneezing, or sore throat | Common | Sometimes |
Sometimes people say that they have a "flu" when they really have something else. For example, "stomach flu" isn't the flu; it's gastroenteritis.
What other problems can the flu cause?
Some people who get the flu will develop complications. Some of these complications can be serious or even life-threatening. They include:
- Bronchitis
- Ear infection
- Sinus infection
- Pneumonia
- Inflammation of the heart (myocarditis), brain (encephalitis), or muscle tissues (myositis, rhabdomyolysis)
The flu also can make chronic health problems worse. For example, people with asthma may have asthma attacks while they have flu.
Certain people are more likely to have complications from the flu, including:
- Adults 65 and older
- Pregnant women
- Children younger than 5
- People with certain chronic health conditions, such as asthma, diabetes, and heart disease
How is the flu diagnosed?
To diagnose the flu, health care providers will first do a medical history and ask about your symptoms. There are several tests for the flu. For the tests, your provider will swipe the inside of your nose or the back of your throat with a swab. Then the swab will be tested for the flu virus.
Some tests are quick and give results in 15-20 minutes. But these tests are not as accurate as other flu tests. These other tests can give you the results in one hour or several hours.
What are the treatments for the flu?
Most people with the flu recover on their own without medical care. People with mild cases of the flu should stay home and avoid contact with others, except to get medical care.
But if you have symptoms of flu and are in a high risk group or are very sick or worried about your illness, contact your health care provider. You might need antiviral medicines to treat your flu. Antiviral medicines can make the illness milder and shorten the time you are sick. They also can prevent serious flu complications. They usually work best when you start taking them within 2 days of getting sick.
Can the flu be prevented?
The best way to prevent the flu is to get a flu vaccine every year. But it's also important to have good health habits like covering your cough and washing your hands often. This can help stop the spread of germs and prevent the flu.
Centers for Disease Control and Prevention
Symptoms
- Flu Symptoms and Complications (Centers for Disease Control and Prevention) Also in Spanish
Diagnosis and Tests
- Diagnosing Flu (Centers for Disease Control and Prevention) Also in Spanish
-
Flu (Influenza) Test
(National Library of Medicine) Also in Spanish
-
Nasal Swab
(National Library of Medicine) Also in Spanish
Prevention and Risk Factors
- Flu: Preventive Actions (Centers for Disease Control and Prevention) Also in Spanish
- Healthy Habits to Help Protect against Flu (Centers for Disease Control and Prevention) Also in Spanish
- Influenza Prevention: Information for Travelers (Centers for Disease Control and Prevention) Also in Spanish
- Preventing the Flu (American Academy of Family Physicians) Also in Spanish
Treatments and Therapies
-
5 Tips: Natural Products for the Flu and Colds: What Does the Science Say?
(National Center for Complementary and Integrative Health)
- Decongestants: OTC Relief for Congestion (American Academy of Family Physicians) Also in Spanish
-
Echinacea
(National Center for Complementary and Integrative Health)
-
Elderberry
(National Center for Complementary and Integrative Health)
-
Flu and Colds: In Depth
(National Center for Complementary and Integrative Health) Also in Spanish
- People at Higher Risk of Flu Complications (Centers for Disease Control and Prevention) Also in Spanish
- Protect Your Family from Fraudulent Flu Products (Food and Drug Administration) Also in Spanish
- Treating Influenza (Flu) (Centers for Disease Control and Prevention) - PDF
- What are Flu Antiviral Drugs (Centers for Disease Control and Prevention) Also in Spanish
Living With
- Caring for Someone Sick (Flu) (Centers for Disease Control and Prevention) Also in Spanish
- Flu: What to Do If You Get Sick (Centers for Disease Control and Prevention) Also in Spanish
Related Issues
- Cancer, Flu, and You (Centers for Disease Control and Prevention) Also in Spanish
- Flu and People Living with HIV (Centers for Disease Control and Prevention) Also in Spanish
- Flu and People with Asthma (Centers for Disease Control and Prevention) Also in Spanish
- Flu and People with Diabetes (Centers for Disease Control and Prevention) Also in Spanish
- Flu and People with Heart Disease or History of Stroke (Centers for Disease Control and Prevention) Also in Spanish
-
Is It Flu, COVID-19, Allergies, or a Cold?
(National Institutes of Health) Also in Spanish
- Seasonal Flu and Staph Infection (Centers for Disease Control and Prevention) Also in Spanish
Specifics
- Understanding Flu Viruses (Centers for Disease Control and Prevention) Also in Spanish
Images
- Influenza Photos (Immunization Action Coalition)
Health Check Tools
- FluView (Centers for Disease Control and Prevention)
Test Your Knowledge
- Test Your Flu Prevention Knowledge (Medical Encyclopedia) Also in Spanish
Statistics and Research
- Weekly U.S. Influenza Surveillance Report (Centers for Disease Control and Prevention)
Clinical Trials
-
ClinicalTrials.gov: Influenza, Human
(National Institutes of Health)
Journal Articles References and abstracts from MEDLINE/PubMed (National Library of Medicine)
- Article: Lot-to-lot consistency, immunogenicity and safety of a quadrivalent split virion inactivated...
- Article: Multiple vaccine comparison in the same adults reveals vaccine-specific and age-related...
- Article: The role of influenza Hemagglutination-Inhibition antibody as a vaccine mediator in...
- Flu -- see more articles
Children
- Children and Flu Antiviral Drugs (Centers for Disease Control and Prevention) Also in Spanish
- Flu and Children with Neurologic Conditions (Centers for Disease Control and Prevention) Also in Spanish
- Flu: A Guide for Parents of Children or Adolescents with Chronic Health Conditions (American Academy of Pediatrics) Also in Spanish
- Is It a Cold, the Flu, an RSV Infection, or COVID-19? (For Parents) (Nemours Foundation) Also in Spanish
- Protect against Flu: Caregivers of Infants and Young Children (Centers for Disease Control and Prevention) Also in Spanish
- The Flu (For Kids) (Nemours Foundation) Also in Spanish
- The Flu: Should You Go to School? (Nemours Foundation) Also in Spanish
- What to Do About the Flu (Nemours Foundation) Also in Spanish
Women
- Flu and Pregnancy (Centers for Disease Control and Prevention) Also in Spanish
Older Adults
- Flu and People 65 Years and Older (Centers for Disease Control and Prevention) Also in Spanish
- What to Do if You Get the Flu (AGS Health in Aging Foundation)
Patient Handouts
- College students and the flu (Medical Encyclopedia) Also in Spanish
- Flu (Medical Encyclopedia) Also in Spanish
- Pregnancy and the flu (Medical Encyclopedia) Also in Spanish
- Your baby and the flu (Medical Encyclopedia) Also in Spanish
- Your child and the flu (Medical Encyclopedia) Also in Spanish