What Is the Flu Virus?

Learn about the various types of flu strains that you can catch this year. Plus, find out who is most at risk for complications and how to treat symptoms.

Sanaz Majd, MD
4-minute read
Episode #104

It’s that time of year again – when our noses start to drain, our throats feel like we swallowed a golf ball, and our muscles feel like we aged 30 years. Yes, it’s flu season. And not only have I already seen a few patients trickle through with the seasonal flu, but I am also suffering from one right now as I sit down to write and record this episode (cough, cough). And since the flu season has officially begun, I thought now would be a good time to learn more about this nasty bug.

What is the Flu?

What Is the Flu Virus?

The flu is a virus (not bacteria!) that spreads mostly from person to person, and typically around the fall through spring months. There are various types, depending on the type of protein that the virus carries on its capsule, or outer covering. Here are the most common:

  • Influenza A: One type of seasonal flu that occurs in birds and some mammals.

  • Influenza B: Another type of seasonal flu that occurs mainly in mammals and seals.

  • Influenza C: A much rarer type of seasonal flu that can create local epidemics.

  • Avian Flu: Spread from birds to humans in Asia, Africa, and Europe.

  • Swine Flu: Otherwise known as H1N1, it’s spread from pigs to humans in the U.S.

The flu doesn’t typically have long term consequences in most people, and often resolves on its own. However, in rare cases, it can be fatal and causes 10,000 to 50,000 deaths a year. For that reason it’s important to prevent it from spreading as much as possible.

Symptoms of the Flu

Common symptoms of the flu include:

  • Fever
  • Body aches
  • Malaise
  • Headache
  • Fatigue
  • Dry cough
  • Less common symptoms of the flu (and more common in the common cold) are:
  • Runny or stuffy nose
  • Sore throat
  • Sneezing


Please note that all content here is strictly for informational purposes only. This content does not substitute any medical advice, and does not replace any medical judgment or reasoning by your own personal health provider. Please always seek a licensed physician in your area regarding all health related questions and issues.

About the Author

Sanaz Majd, MD

Dr. Sanaz Majd is a board-certified Family Medicine physician who graduated from Drexel University College of Medicine in Philadelphia. Her special interests are women's health and patient education.