If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

Flu Epidemiology

The flu has been causing disease and death for a long time. Get a feel for exactly how many folks are affected each year by this disease. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Stanford School of Medicine.

Want to join the conversation?

Video transcript

Let's imagine that this is you, and you are headed home for the holidays. So you board a plane, and you notice while you're on this plane that the people around you are pretty sick. The guy next to you looks like he has a fever. Maybe the flight attendant is coughing. So you head on home. And although you're excited to see everybody in your family, you are feeling completely run down. And so you decide to head to bed, and hopefully you'll feel better tomorrow. Unfortunately, you don't feel better the next day. You have a very high fever. You don't even have the strength to get out of bed for a few days. And when you finally start to feel better, you notice that you're not the only person in your house who's sick. Your dad is sick. Your mom is sick as well, maybe some of your siblings. You call your best friend. They are sick, and their entire family is sick. Maybe you talk to a neighbor and someone on your street, you learn, has died from this illness. And news reports say that this is not unique to your town, but it's happening all over the state and all over the country. Now, this is a really scary situation. But unfortunately, it's not one that is out of the realm of possibility. In 1918 and 1919, this was a particularly bad influenza season. In fact, it was so bad that it led to approximately 50 to 100 million deaths worldwide. And this is a pretty famous picture from that era of a makeshift hospital. There were so many sick people during this flu season that hospitals couldn't provide enough beds and resources for the patients who needed it. Even during a so-called regular flu season, every year the influenza virus causes a lot of damage. Flu is a top 10 killer in the United States, and it leads to approximately 200,000 hospitalizations every year due to complications of the influenza virus. In addition to the 200,000 hospitalizations that we have every year in this country, approximately 20,000 to 40,000 people die every single year, 20,000 to 40,000 deaths on an annual basis. So you can see that influenza is not something to be taken lightly, but can lead to very serious consequences. But luckily, there is something that can be done. In fact, there's something that you can do about this. As someone who's learning this training, you're learning how to vaccinate people in your community. The modern influenza vaccine is approximately 70% effective in preventing influenza infection, and so this is a great way to help prevent illness and death.