What Is Influenza?
Influenza, commonly called the flu, is a contagious respiratory illness caused by influenza viruses. It affects the nose, throat, and lungs and can range from a mild illness to a serious infection requiring hospitalization.
The flu spreads easily from person to person through respiratory droplets released when someone coughs, sneezes, talks, or breathes. Unlike the common cold, the flu often comes on suddenly and commonly causes fever, chills, muscle aches, fatigue, and cough.
Most healthy people recover within one to two weeks, but influenza can lead to serious complications such as pneumonia, worsening of chronic medical conditions, hospitalization, or even death, particularly in older adults, young children, pregnant individuals, and people with weakened immune systems.
Annual influenza vaccination is the best way to reduce your risk of getting the flu and developing serious complications.
Learn More
Influenza (Flu) – NIH MedlinePlus
https://medlineplus.gov/flu.html
Provides easy-to-understand information about influenza, symptoms, diagnosis, treatment, and prevention.
Influenza (Flu) – Centers for Disease Control and Prevention (CDC)
https://www.cdc.gov/flu/
Provides comprehensive information about seasonal influenza, vaccination, treatment, and prevention.
How Common Is Influenza?
Influenza affects millions of people each year in the United States. Flu activity usually increases during the fall and winter months, with peak activity often occurring between December and February, although cases can occur throughout the year.
Each flu season varies in severity depending on the circulating influenza viruses and vaccination rates.
Learn More
CDC Flu Season Information
https://www.cdc.gov/flu/
Provides current information about seasonal influenza activity and prevention.
What Symptoms Might You Notice?
Flu symptoms usually begin suddenly and are often more severe than those of the common cold.
Common symptoms include:
- Fever
- Chills
- Cough
- Sore throat
- Runny or stuffy nose
- Muscle aches
- Body aches
- Headache
- Fatigue
- Weakness
- Loss of appetite
Some people, especially children, may also experience:
- Nausea
- Vomiting
- Diarrhea
How Is Influenza Diagnosed?
Your healthcare provider will review your symptoms, recent exposures, and perform a physical examination.
During flu season, influenza may be diagnosed based on symptoms alone. Laboratory testing may be recommended if the diagnosis is uncertain or if antiviral treatment is being considered.
Learn More
Influenza (Flu) – NIH MedlinePlus
https://medlineplus.gov/flu.html
Explains how influenza is diagnosed and when testing may be recommended.
Influenza (Flu) infographic – click to enlarge
What Causes Influenza?
Influenza is caused by influenza viruses, most commonly Influenza A and Influenza B.
The virus spreads through:
- Coughing
- Sneezing
- Talking
- Close contact with infected individuals
- Touching contaminated surfaces and then touching your eyes, nose, or mouth
People may spread influenza beginning about one day before symptoms develop and for several days after becoming sick.
Learn More
Influenza (Flu) – CDC
https://www.cdc.gov/flu/
Learn how influenza spreads and ways to reduce your risk.
What Can Make Influenza Worse?
Certain individuals are at higher risk for severe illness and complications.
Risk factors include:
- Age 65 years or older
- Children younger than 5 years (especially under 2 years)
- Pregnancy
- Asthma
- COPD
- Heart disease
- Diabetes
- Chronic kidney disease
- Weakened immune system
- Obesity
- Smoking or vaping
Learn More
People at Higher Risk for Flu Complications – CDC
https://www.cdc.gov/flu/highrisk/
Provides information about people at increased risk for severe influenza illness.
Prevention
The best way to prevent influenza is through annual vaccination and healthy infection-prevention practices.
Helpful prevention tips include:
- Receive your influenza vaccine every year.
- Wash your hands frequently with soap and water.
- Avoid touching your eyes, nose, and mouth.
- Cover coughs and sneezes.
- Stay home when you are sick.
- Avoid close contact with people who are ill.
- Clean frequently touched surfaces regularly.
- Maintain healthy habits that support your immune system.
Learn More
Preventing Seasonal Flu – CDC
https://www.cdc.gov/flu/prevention/
Provides practical recommendations for preventing influenza and reducing transmission.
Learn More About Influenza
The following video content is provided to help you better understand this condition. These resources are intended for educational purposes and should not replace personalized medical advice from your healthcare provider.
Labs
Laboratory testing depends on your symptoms and overall health.
Common laboratory tests may include:
- Rapid Influenza Diagnostic Test (RIDT): Provides quick results for influenza A and B.
- Influenza PCR Test: Highly accurate test used to confirm influenza infection.
- Complete Blood Count (CBC): May help evaluate infection or complications.
- Comprehensive Metabolic Panel (CMP): May assess hydration status and organ function in more severe illness.
Learn More
Laboratory Testing – CDC
https://www.cdc.gov/flu/
Provides information about influenza testing and diagnosis.
Diagnostics
Additional testing depends on the severity of illness and whether complications are suspected.
Common diagnostic tests may include:
- Chest X-ray: May identify pneumonia or other lung complications.
- Pulse Oximetry: Measures oxygen levels in the blood.
- Respiratory Viral Panel: May identify influenza along with other respiratory viruses.
- Polymerase Chain Reaction (PCR) Testing: Highly accurate testing for influenza viruses.
Learn More
Influenza (Flu) – CDC
https://www.cdc.gov/flu/
Provides information about influenza testing and evaluation.
Treatment & Management
Treatment Options
Treatment depends on the severity of illness, your overall health, and how long you have been sick.
Treatment options may include:
- Rest
- Drinking plenty of fluids
- Fever and pain medications
- Prescription antiviral medications when appropriate
- Hospitalization for severe illness
- Oxygen therapy if needed
Antiviral medications work best when started within 48 hours after symptoms begin, although they may still benefit certain high-risk individuals even if started later.
Learn More
Treating Flu with Antiviral Drugs – CDC
https://www.cdc.gov/flu/treatment/
Provides information about antiviral medications and supportive care.
Lifestyle Changes
Healthy habits help support recovery and reduce the spread of influenza.
Helpful lifestyle changes include:
- Get plenty of rest.
- Drink plenty of fluids.
- Eat nutritious foods as tolerated.
- Stay home while you are sick.
- Wash your hands frequently.
- Cover coughs and sneezes.
- Avoid smoking and vaping.
- Stay up to date on your annual influenza vaccine.
Learn More
Influenza (Flu) – CDC
https://www.cdc.gov/flu/
Provides recommendations for recovering safely and preventing the spread of influenza.
Medications
Treatment depends on your symptoms, risk factors, and how early treatment begins.
Common medications may include:
- Acetaminophen: Helps reduce fever and relieve pain.
- Ibuprofen or Naproxen: Help reduce fever, inflammation, and body aches (when appropriate).
- Oseltamivir (Tamiflu®): The most commonly prescribed antiviral medication for influenza.
- Zanamivir (Relenza®): An inhaled antiviral medication used for certain patients.
- Baloxavir Marboxil (Xofluza®): A single-dose antiviral medication for eligible patients.
- Peramivir (Rapivab®): An intravenous antiviral medication used in selected situations.
Antibiotics do not treat influenza unless a bacterial infection develops in addition to the flu.
Learn More
Treating Flu with Antiviral Drugs – CDC
https://www.cdc.gov/flu/treatment/
Provides information about antiviral medications and influenza treatment.
Procedures
Most people with influenza do not require surgery or invasive procedures. Treatment usually focuses on relieving symptoms while the immune system clears the infection. However, supportive treatments or hospital-based procedures may be necessary if severe illness or complications develop.
Common procedures may include:
- Oxygen Therapy: May be needed if influenza causes low oxygen levels or difficulty breathing.
- Intravenous (IV) Fluids: Used to treat dehydration caused by fever, poor fluid intake, vomiting, or diarrhea.
- Nebulizer Treatments: May help relieve wheezing or breathing difficulties in people with asthma, COPD, or other underlying lung conditions.
- Hospital Monitoring: Severe influenza may require hospitalization for oxygen therapy, medications, close monitoring, or intensive care.
Learn More
Influenza (Flu) – Centers for Disease Control and Prevention (CDC)
https://www.cdc.gov/flu/
Learn about influenza treatment, supportive care, and hospitalization.
What Should You Expect Long-Term?
Most healthy people recover from influenza within 1 to 2 weeks, although fatigue and a lingering cough may continue for several weeks.
Some individuals, especially older adults, young children, pregnant individuals, and people with chronic medical conditions, are at greater risk of complications such as:
- Pneumonia
- Ear infections
- Sinus infections
- Dehydration
- Worsening asthma or COPD
- Worsening heart disease
Follow up with your healthcare provider if symptoms persist or worsen.
What Can You Do At Home?
Home care is one of the most important parts of recovering from influenza.
Helpful tips include:
- Get plenty of rest.
- Drink plenty of fluids.
- Eat nutritious foods as tolerated.
- Take fever and pain medications as directed.
- Stay home until your fever has been gone for at least 24 hours without using fever-reducing medication and you are feeling well enough to resume normal activities.
- Wash your hands frequently.
- Cover coughs and sneezes.
- Avoid smoking and vaping.
- Follow your healthcare provider’s recommendations regarding antiviral medications.
Learn More
Treating Flu – CDC
https://www.cdc.gov/flu/treatment/
Provides practical recommendations for recovering safely from influenza.
Frequently Asked Questions
Is the flu different from the common cold?
Yes. Influenza usually begins suddenly and often causes higher fever, more severe body aches, greater fatigue, and a more intense cough than the common cold.
Do antibiotics treat influenza?
No. Antibiotics only treat bacterial infections. They do not work against influenza viruses unless you also develop a bacterial infection.
How long am I contagious?
Most adults can spread influenza beginning about
one day before symptoms start
and for
5–7 days after becoming sick
. Children and people with weakened immune systems may remain contagious longer.
Should I get a flu vaccine every year?
Yes. Annual influenza vaccination is recommended for nearly everyone
6 months of age and older
, unless there is a medical reason not to receive it.
When should antiviral medication be started?
Antiviral medications work best when started within
48 hours
of symptom onset, although they may still benefit some people at higher risk for complications if started later.
Questions To Ask Your Provider
Consider asking your healthcare provider:
- Do I need antiviral medication?
- Am I at high risk for flu complications?
- How long should my symptoms last?
- When can I safely return to work, school, or other activities?
- What symptoms should prompt me to seek medical care?
- When should I receive my next influenza vaccine?
- How can I reduce the risk of spreading influenza to others?
Specialist Referrals
Most cases of influenza are managed by a primary care provider. Depending on the severity of your illness or underlying medical conditions, your provider may recommend seeing a specialist.
You may be referred to:
- Primary Care Provider: Coordinates diagnosis, treatment, and follow-up care.
- Pulmonologist: Evaluates pneumonia, asthma, COPD, or other lung complications.
- Infectious Disease Specialist: Evaluates severe, prolonged, or unusual influenza infections.
- Hospital Medicine or Critical Care Specialist: Provides care for patients requiring hospitalization or intensive care.
Learn More
Influenza (Flu) – CDC
https://www.cdc.gov/flu/
Provides information about influenza complications and specialty care.
Is Influenza Curable?
Yes. Influenza is usually a self-limited illness, meaning your immune system clears the virus over time. Most people recover completely with rest, fluids, supportive care, and, when appropriate, antiviral medication.
Receiving the annual influenza vaccine is the best way to reduce your risk of becoming infected and developing serious complications.
Emergency Symptoms / When To Seek Immediate Help
Call 911 or seek emergency medical care immediately if you experience:
- Difficulty breathing or severe shortness of breath
- Chest pain
- Blue lips or fingertips
- Confusion or difficulty waking up
- Loss of consciousness
- Seizures
- Persistent high fever with severe illness
- Severe dehydration (very little urine, dizziness, inability to keep fluids down)
Seek prompt medical evaluation if you notice:
- Fever that improves and then returns
- Symptoms lasting longer than expected
- Persistent vomiting
- Worsening cough
- Difficulty breathing during routine activities
- Symptoms that continue to worsen instead of improving
Learn More
Emergency Warning Signs of Flu – CDC
https://www.cdc.gov/flu/
Learn how to recognize serious influenza complications and when emergency medical care is needed.
CALL 911
APNS does not provide emergency medical services. If you believe you are experiencing a medical emergency, including (but not limited to) chest pain, difficulty breathing, stroke symptoms, severe allergic reactions, anaphylaxis, uncontrolled bleeding, seizures, loss of consciousness, or any other potentially life-threatening condition, you are instructed to call 911 immediately or go immediately to the nearest emergency department.
Official Resources / External Links
Influenza (Flu) – NIH MedlinePlus
https://medlineplus.gov/flu.html
Easy-to-understand information about influenza, symptoms, diagnosis, treatment, and prevention.
Influenza (Flu) – Centers for Disease Control and Prevention (CDC)
https://www.cdc.gov/flu/
Comprehensive information about seasonal influenza, vaccination, antiviral medications, and prevention.
Treating Flu with Antiviral Drugs – CDC
https://www.cdc.gov/flu/treatment/
Reliable information about influenza treatment, antiviral medications, and supportive care.
American Lung Association
https://www.lung.org/
Evidence-based information about influenza, pneumonia, respiratory health, and lung disease.
This guide is intended for educational purposes only and should not replace medical advice, diagnosis, or treatment from your healthcare provider. Always follow the recommendations of your healthcare team regarding your individual health needs. Contact your healthcare provider if your symptoms worsen, new symptoms develop, or do not improve as expected. Call 911 immediately if you experience difficulty breathing, chest pain, blue lips, confusion, loss of consciousness, seizures, severe dehydration, or another medical emergency.
Get personalized care for Influenza
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