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What Causes the Flu?

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Why Do People Usually Get the Flu in Winter?

Flu outbreaks occur more frequently in the winter months. Many factors may play a role in the flu's seasonal pattern including. Here's why:

  • The flu virus survives for longer periods indoors in winter because the relative humidity of indoor air is very low in comparison to the outside air.
  • The flu virus may stay suspended in the air for prolonged periods and thus infect others by being inhaled. The flu virus droplets can also infect by landing on sensitive body areas such as the eyes, nose, or mouth.
  • In winter, humans tend to be indoors more and thus have closer contact with each other, which makes it easier for the flu virus to spread.

How Long Am I Contagious After I Get the Flu?

You are contagious for up to seven days after the onset of the flu, although the flu virus can be detected in secretions up to 24 hours before the onset of symptoms. This means you might transmit the flu virus a full day before your flu symptoms begin.

In young children, the flu virus can still be spread in the secretions even into the second week of illness.

How Can I Prevent the Flu?

To prevent the flu, be sure to keep your hands clean -- wash them frequently to remove germs -- and get a flu shot. The CDC develops a flu vaccine based on the type A strain that they believe will be most prevalent in the coming flu season. This is the vaccine you get with the annual flu shot or FluMist nasal spray.

For in-depth information, see WebMD's Flu Shot: Influenza Vaccine.

Also, see WebMD's What Is FluMist?

WebMD Medical Reference

Reviewed by Kimball Johnson, MD on June 11, 2012
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