Influenza is a viral infection of the nose, throat, bronchial tubes and lungs. There are two main types of virus: influenza A and influenza B. Each type includes many different strains, which tend to change each year. Seasonal influenza sometimes causes severe illness or complications, but the great majority of people recover fully without any medical treatment.
When does influenza occur?
Influenza is most common during the fall and winter months. Flu activity often increases during the late fall and early winter in the United States, but peak levels generally occur between late December and early March. Illnesses resembling influenza may occur during the summer months but they are usually due to other viruses.
Who gets influenza?
Anyone can get influenza, but it is most serious in the elderly, in young children, in people with chronic underlying health conditions such as asthma, diabetes or a weakened immune system.
How is influenza spread?
Influenza is highly contagious and easily transmitted through contact with droplets from the nose and throat of an infected person during coughing and sneezing.
What are the symptoms of influenza?
Typical symptoms include fever, chills, aches, cough and sore throat. Intestinal symptoms, such as vomiting or diarrhea, are possible but uncommon. Although most people are ill for only a few days, influenza sometimes leads to more serious illness, such as pneumonia. Influenza-related illness, including pneumonia, causes approximately 36,000 deaths in the United States each year. Here in New York City, influenza causes an estimated 1,100 deaths, and respiratory infections cause more than 2,000.
How soon after infection do symptoms appear?
Influenza generally occurs within 1 to 4 days after exposure.
How is influenza diagnosed?
Doctors diagnose influenza by checking for common symptoms such as fever, chills, aches, cough and sore throat. Lab tests are sometimes used to confirm the diagnosis, but these tests are not necessary or useful in most instances.
What should I do if I get flu-like symptoms?
Most people recover from flu on their own, without medical treatment. They don’t need to go to the hospital, but they do need to take steps to avoid spreading the infection. If you have a fever (100 degrees or higher), plus a cough or sore throat, be sure to take these steps:
When should I call a doctor?
Some people are more likely than others to get very sick with the flu. People who have flu-like symptoms or have had recent close contact with someone with flu-like symptoms should call a health care provider if they belong to any of these higher risk groups:
What is the treatment for influenza?
Rest and liquids are usually adequate, but antiviral medication can help prevent severe illness and complications in people at high risk. Four antiviral drugs – amantadine, rimantidine, zanamivir and oseltamivir – are available by prescription.
When should I go to the hospital?
Go to the hospital or call 911 right away if you have trouble breathing or experience any of these other severe symptoms:
How can I protect myself from influenza?
Getting vaccinated is the best way to avoid influenza. Influenza vaccines (flu shots) are available from private health care providers, from Health Department immunization clinics, and from most pharmacies.
Does past infection with influenza make a person immune?
The viruses that cause influenza frequently change, so people who have been infected or immunized in previous years may become infected with a new strain. To maintain your immunity, you need to get a seasonal influenza vaccine each year.
Who should get vaccinated against seasonal influenza?