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Influenza (flu)

Flu is a contagious respiratory illness caused by influenza viruses that infect the respiratory tract. Flu illness can be mild to severe and in some cases may even cause death. Although anyone can become infected with flu, people 65 years and older, young children, and people with other health conditions are at higher risk for hospitalization and complications from flu. The best way to reduce the risk of flu and its complications is by getting vaccinated every year.

Frequently Asked Questions

  • What are the signs and symptoms of influenza?

    Symptoms usually include:

    • Fever
    • Chills
    • Headache
    • Cough
    • Sore throat
    • Muscle aches
    • Diarrhea and nausea occasionally in children

    Symptoms usually start about 1-4 days after being exposed and can last 2-7 days. Complications may include pneumonia, hospitalization and death.

  • How does influenza spread?

    Flu is spread from close contact with persons who are sick with flu or from touching surfaces or objects that have flu virus on them. Infection can occur when flu viruses contact the eyes, mouth, or nose, and through breathing in droplets from a sneeze or cough.

    People may be able to spread the virus to others about one day before they show symptoms and up to seven days after becoming sick. That means that you may be able to spread the flu to someone else before you even know you are sick, as well as while you are sick.

  • Who is at risk for influenza infection?

    In the United States, on average 5% to 20% of the population gets the flu and more than 200,000 people are hospitalized from seasonal flu-related complications. Some people, such as older people, young children, pregnant women, and people with certain health conditions, are at high risk for serious flu complications. These health conditions include:

    • Asthma
    • Neurological and neurodevelopmental conditions
    • Chronic lung disease
    • Heart disease
    • Blood disorders
    • Endocrine disorders (i.e., diabetes)
    • Kidney and liver disorders
    • Metabolic disorders
    • Weakened immune systems due to medication or disease, such as HIV/AIDS
    • People younger than 19 years of age receiving long-term aspirin therapy
    • People who are morbidly obese
  • How do I know if I have influenza?

    A health care professional may be able to diagnose a flu infection by looking at your symptoms. Sometimes your nose will be swabbed and tested for the influenza virus.

  • How is influenza treated?

    Flu is usually treated with medicine to bring down the fever, throat or cough drops, water, and plenty of rest. If the diagnosis is made at the very beginning of the illness, a doctor may prescribe influenza antiviral medicine (i.e., oseltamivir, zanamivir, or peramavir).

  • How is influenza prevented?

    The best way not to get flu is to get a flu shot every year before the flu season starts.

    Since flu viruses change over time, it is important to get a shot each year. Each year the vaccine is remade to include the types of flu viruses scientist think will be around to cause illness during the flu season. The vaccine begins to protect you within a few days after you get the flu shot, but the vaccine is not fully effective until about 14 days after the shot.

    Good respiratory hygiene is important to prevent the spread of all respiratory infections, including the flu:

    • Use your elbow or upper arm, instead of your hands, or a tissue to cover your mouth and nose or when you cough or sneeze. Immediately throw used tissues into the trash can. Try not to touch your eyes, nose, or mouth. Many diseases often spread this way. *
    • Clean your hands after coughing or sneezing. Wash with soap and water, or clean with alcohol-based hand cleaner if water is not available.
    • Avoid close contact with people who are sick.
    • If you get flu, stay home from work, school, and social gatherings. This will help others from catching your illness and gives your body the rest it needs to get better.

Information for the Public

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Information for Clinicians

Laboratory Specimen Information
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Sentinel Sites

Outpatient Influenza-like Illness Sentinel Surveillance Network (ILINet) is a surveillance program with participating healthcare providers from outpatient clinics. Data reported by the sentinel providers is used to determine the burden of influenza in the state.