Columbia, SC (WLTX) - How long are you contagious if you have the flu? Some say a few days while others argue that you can spread the virus even after a week, so which is true?

The answer isn't so simple.

Eric Brenner, M.D. works at the University of South Carolina's Arnold School of Public Health and specializes in infectious diseases.

"Most people are maybe infectious only for about 3 or 4 or 5 days, perhaps a week at the most and people start to become infectious even the day before they start to become sick. That's a bit tricky because they don't know that they are sick and maybe they aren't taking precautions then," Brenner said. "Little kids sometimes, especially grammar school kids may be infectious for several more days maybe up to a week or more. That's why it's good to keep your kids home from school, maybe not just for two or three days, but for that whole week."

As for when to return to work or school, Brenner said to use common sense.

"Where do you work? How many people are working with you? If you work outdoors or you are a gardener let's say or a telephone repairman and you're up on a telephone pole, even if you cough up there, you are not going to transmit influenza to anybody," he said.

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