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Facts About Flu

What to know about the flu

Know what causes the flu

The flu is a contagious illness caused by any of several types of influenza viruses. The virus infects the respiratory system—the nose, throat, and lungs.

There are 4 types of influenza virus: A, B, C, and D. According to the Centers for Disease Control and Prevention (CDC), types A and B are responsible for seasonal flu epidemics.

TYPE A is the most common form—and often the most harmful. Subtypes of type A have caused some of the deadliest flu pandemics in history
TYPE B is also highly contagious and can cause outbreaks of seasonal flu

For more details about the influenza virus, visit the CDC website.

4 types of Influenza virus

There are 4 types of influenza virus: A, B, C, and D. According to the Centers for Disease Control and Prevention (CDC), types A and B are responsible for seasonal flu epidemics.

TYPE A is the most common form—and often the most harmful. Subtypes of type A have caused some of the deadliest flu pandemics in history
TYPE B is also highly contagious and can cause outbreaks of seasonal flu

For more details about the influenza virus, visit the CDC website.

Know when flu season starts

In the United States, flu season starts in the fall and lasts through the winter. Flu activity typically peaks between December and February, but it can last until May.

The CDC monitors flu activity year-round and reports on what viruses are circulating and the incidence of flu-related complications. For the most recent information, visit the CDC website.

Know how the flu spreads

Flu viruses travel through the air in droplets when someone with the infection coughs, sneezes, or talks. You can become infected when you inhale the droplets directly or pick up the germs from touching an object and then touching your eyes, nose, or mouth.

To lower your chance of infection, avoid contact with people who have the flu and wash your hands frequently.

Know how COVID-19 differs from the flu

Although COVID-19 and the flu may have some symptoms in common, they are 2 distinct illnesses. They are caused by different viruses and require different vaccines—and both can be life threatening. Visit the CDC website CDC website to learn more about COVID-19.

Warning signs of a potential flu emergency

People experiencing any of these warning signs should obtain medical care right away.

Difficulty breathing or shortness of breath
Persistent pain or pressure in the chest or abdomen
Persistent dizziness, confusion, or inability to arouse
Seizures
Not urinating
Severe muscle pain
Severe weakness or unsteadiness
Fever or cough that improve but then return or worsen
Worsening of chronic medical conditions
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Know how to help protect yourself and your family from the flu

The flu is a serious illness that can have serious, even deadly, consequences.

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FLU SHOT LOCATOR

What are FLUBLOK® QUADRIVALENT (INFLUENZA VACCINE) and FLUZONE® HIGH-DOSE QUADRIVALENT (INFLUENZA VACCINE)?

Flublok Quadrivalent and Fluzone High-Dose Quadrivalent are indicated for immunization against disease caused by influenza A and B strains contained in the vaccine. Flublok Quadrivalent is given to people 18 years of age and older. Fluzone High-Dose Quadrivalent is given to people 65 years of age and older.

IMPORTANT SAFETY INFORMATION

Flublok Quadrivalent and Fluzone High-Dose Quadrivalent should not be given to anyone who has had a severe allergic reaction to any component of the vaccine (including eggs or egg products for Fluzone High-Dose Quadrivalent). In addition, Fluzone High-Dose Quadrivalent should not be given to anyone who has had a severe allergic reaction after previous dose of any influenza vaccine.

Tell your health care provider if you have ever had Guillain-Barré syndrome (severe muscle weakness) after a previous influenza vaccination.

If Flublok Quadrivalent and Fluzone High-Dose Quadrivalent are given to people with a compromised immune system, including those receiving therapies that suppress the immune system, the immune response may be lower than expected.

Vaccination with Flublok Quadrivalent and Fluzone High-Dose Quadrivalent may not protect all people who receive the vaccine.

For Flublok Quadrivalent, in adults 18 through 49 years of age, the most common side effects were tenderness, and/or pain where you got the shot; headache, tiredness, muscle aches, and joint pain. In adults 50 years of age and older the most common side effects were tenderness, and/or pain where you got the shot; headache, and tiredness.

For Fluzone High-Dose Quadrivalent, in adults 65 years of age and older, the most common side effects were pain, redness, and/or swelling where you got the shot; muscle aches, headache, and general discomfort.

For Flublok Quadrivalent and Fluzone High-Dose Quadrivalent, other side effects may occur.

For more information, talk to your health care professional and refer to the full Prescribing Information for Flublok Quadrivalent or Fluzone High-Dose Quadrivalent. Also, please see complete Patient Information for Fluzone High-Dose Quadrivalent.