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
hospitalizations and deaths. For the most recent
information, visit the
CDC website.
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 in adults—and often the
most harmful. Subtypes of type A have caused some of the
deadliest flu pandemics in history
TYPE B is also contagious and can cause
outbreaks of seasonal flu
For more details about the influenza virus, visit the CDC website.
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 in adults—and often the
most harmful. Subtypes of type A have caused some of the deadliest
flu pandemics in history
TYPE B is also contagious and can cause outbreaks of
seasonal flu
For more details about the influenza virus, visit the CDC website.
Know when flu season starts.
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 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
Severe weakness or unsteadiness
Fever or cough that improve but then return or worsen
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.
Find your Sanofi flu shot.
Demand more from your flu shot.
Schedule your Sanofi flu vaccine.
Sanofi does not provide medical advice, diagnosis, or treatment. The health information contained herein is provided for general educational purposes only. The best source of information regarding your health is your health care professional, who should be consulted if you have any questions.
