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Cold, Flu, & Cough Health Center

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Understanding the Common Cold -- the Basics

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A runny nose, scratchy throat, and nonstop sneezing -- you can't miss the signs of a cold. But mystery shrouds a lot of other things about it. Why do you seem to get them so often while your best friend stays well? And more importantly, how can you stay healthy this year? Get the lowdown on the all too common cold.

What Is It?

It's an illness caused by a tiny, living thing called a virus. More than 200 types lead to your misery, but the most common one is the rhinovirus, which brings on 10% to 40% of colds. The coronavirus is responsible for about 20% of cases, while the respiratory syncytial virus (RSV) and parainfluenza virus cause 10% of colds.

Colds cause a lot of people to stay home. The CDC says 22 million school days are lost each year in the U.S. because of them. Some estimates say that Americans have 1 billion colds a year.

For more detail, see Common Cold Causes.

How a Common Cold Starts

You can catch it from another person who is infected with the virus. This usually happens if you touch a surface that has germs on it -- a computer keyboard, doorknob, or spoon, for example -- and then touch your nose or mouth. You can also catch it if you're near someone who is sick and sneezes into the air.

A cold begins when a virus attaches to the lining of your nose or throat. Your immune system -- the body's defense against germs -- sends out white blood cells  to attack this invader. Unless you've had a run-in with that exact strain of the virus before, the initial attack fails and your body sends in reinforcements. Your nose and throat get inflamed and make a lot of mucus. With so much of your energy directed at fighting the cold virus, you're left feeling tired and miserable.

One myth that needs to get busted: Getting chilly or wet doesn't cause you to get sick. But there are things that make you prone to come down with a cold. For example, you're more likely to catch one if you're extremely tired, under emotional distress, or have allergies with nose and throat symptoms.

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