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Vitamins and medicines for colds are displayed at a pharmacy in Paris on Nov. 27, 2017.

If you think you're coming down with the flu, here's advice from all of us: Stay home.

Sick employees could wind up costing employers $9 billion in lost productivity, according to Challenger, Gray & Christmas, Inc., an executive coaching firm that crunched the stats.

“The current strain is particularly aggressive and those who are sick can be contagious for up to seven days. Workers who have the flu or need to care for someone with the flu should absolutely not come into work," Andrew Challenger, the firm's vice president of global outplacement consultancy, said in a statement. "This is exactly why employers have sick leave benefits."