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How Long Is the Flu Contagious?

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Updated March 29, 2012

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

None of us want to get the flu, but when it pops up somewhere it seems to spread like wildfire. One person in your office comes into work sick and the next thing you know, half of the employees are calling in sick or coughing and sneezing at their desks.

How Long Is the Flu Contagious?

Contagious means that an illness can pass from one person to another making them sick. How contagious a person is depends on the virus or bacteria that is making them sick.

If you truly have influenza -- the flu -- it is typically considered to be contagious from one day before you develop symptoms through 5 to 7 days after symptoms start.

To make matters a little more complicated, kids can spread the virus for longer -- more than 7 days in some cases.

One of the reasons the flu spreads so rapidly is because it is contagious before you know you have it. That means you could be exposed to the virus one day, two days later you are spreading it to other people around you, but you don't get that "hit by a truck" feeling until the third day.

Sources:

"How Flu Spreads" Seasonal Influenza (Flu) 30 Jun 11. US Centers for Disease Control and Prevention. 22 Mar 12.

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