Flu: Symptoms, Treatment and Prevention

An older masked patient smiles and holds up her sleeve to show a Band-Aid she got after a vaccination.

OHSU experts say everyone who is eligible should get the flu vaccine each year.

Find a flu shot near you:

What is flu?

Flu, short for influenza, is an infection in the nose, throat and lungs. Multiple flu viruses circulate every year among humans.  

Many people who get the flu will recover within a week and won’t need medical attention. But the flu can cause serious complications for babies, older adults and people with chronic health conditions or weakened immune systems (immunocompromised).

Preventing flu

OHSU experts say the best way to prevent flu is to get a flu shot, available for ages 6 months and older. People who are pregnant or have babies under 6 months can protect their babies by getting a flu shot for themselves.

Health experts also suggest:

  • Covering coughs and sneezes.
  • Avoiding sick people.
  • Washing your hands often.
  • Not touching your face.
  • Cleaning and disinfecting often-used surfaces.
  • Wearing a face mask.

Flu vaccines are updated every year. Researchers pick the flu viruses they think will be most common in the next flu season. Vaccines use weakened or “killed” versions of those viruses. Vaccines cannot give you the flu.

This year's flu vaccine is quadrivalent, meaning it protects against four of the most common flu viruses.

When you get vaccinated, your immune system learns how to fight these viruses. You don’t have the vaccine’s maximum protection until two weeks after you are vaccinated. But people who get flu shots are less likely to:

  • Have serious symptoms or complications if they get the flu.
  • Spread the flu.
  • Have the flu and COVID -19 at the same time.

    Side effects are usually mild and go away in a few days:

    • Soreness, redness or swelling where the vaccine was given
    • Headache
    • Fever
    • Nausea
    • Muscle pain

    Very rarely, people have allergic reactions to a flu vaccine:

    • Trouble breathing
    • Hoarseness or wheezing
    • Swelling around the eyes or lips
    • Hives
    • Paleness
    • Weakness
    • Fast heartbeat
    • Dizziness

    Allergic reactions usually happen within a few minutes or hours. If you have a reaction, get medical care. 

    Report the reaction to the Vaccine Adverse Event Reporting System. Reports help the Centers for Disease Control and Prevention and the Food and Drug Administration track potential problems with vaccines.

    Flu symptoms

    Flu symptoms start suddenly and last up to a week. They include:

    • Headache
    • Sneezing
    • Stuffy or runny nose
    • Being tired
    • Sore throat
    • Body aches
    • Cough
    • Chills
    • Fever
    • Vomiting (sometimes)
    • Diarrhea (sometimes)

    Learn the difference between symptoms of flu, allergies, colds and COVID-19.

    Flu care and treatment

    Most people need only home care for flu. Flu symptoms usually go away within a week, though you may feel tired and cough for another week or so.

    Care includes:

    • Drinking lots of clear fluids.
    • Taking over-the-counter medications for fever and pain:
      • Acetaminophen (Tylenol)
      • Ibuprofen (Advil, Motrin or PediaCare)
      • Aspirin (Note: adults only.)
    • Resting at home. The CDC suggests staying home for at least 24 hours after a fever goes away without use of medication.

      When to see a doctor for flu

      Doctors can prescribe antiviral drugs for people who:

      • Are in the hospital for flu.
      • Have serious flu symptoms.
      • Are at higher risk of complications and have flu symptoms.

        When to go to the emergency room for flu

        People who have any of these symptoms with flu should get medical care right away:

        • Trouble breathing
        • Chest pain
        • Severe muscle pain
        • Dehydration (dark yellow urine or not urinating)
        • Seizures
        • Fever or cough that improves, then returns or gets worse
        • Chronic (ongoing) medical condition that gets worse

        These symptoms in children and babies need emergency care:

        • Bluish or grayish lips or face, depending on color of skin
        • Fast breathing
        • Ribs pulling in with each breath
        • Not alert or interacting with other people
        • Dehydration:
          • Staying dry or not urinating for more than eight hours
          • Dry mouth
          • No tears when crying
        • Muscle pain:
          • Refusal to walk
          • Crying a lot when picked up
        • Fever:
          • Above 104 degrees
          • Any fever in a baby younger than 3 months (12 weeks)

          Who’s most at risk for flu

          Age and health conditions affect a person’s risk of flu complications. The CDC says people at higher risk include:

          • Children younger than 2
          • Adults 65 and older
          • People who are pregnant or were recently pregnant (within two weeks)
          • People in nursing homes and long-term care
          • People who have:
            • Asthma
            • Blood disorders
            • Chronic lung disease
            • Diabetes
            • Chronic heart disease
            • Kidney disorders
            • Liver disorders
            • Metabolic disorders
            • Obesity (a body mass index of 40 or higher)
            • Weakened immune systems (immunocompromised)
            • Neurologic conditions such as cerebral palsy, epilepsy, stroke, muscular dystrophy or spinal cord injury
            • Developmental delays

            Learn more

            Emergency care for flu

            Get care right away for severe symptoms, including:

            • Trouble breathing
            • Chest pain
            • Severe muscle pain
            • Seizures

            And if a child has:

            • Bluish lips or face
            • Fast breathing
            • Ribs pulling in with each breath
            • Fever above 104 degrees, or any fever for a baby younger than 3 months

              Care at OHSU

              Vaccines at OHSU

              Make an appointment for a:

              • Flu vaccine
              • COVID-19 vaccine
              • Many other vaccines