Employers are not doing a good job of encouraging workers to stay home when they are sick.

Nearly 80 percent of office workers recently surveyed said they come to work when they are sick, an increase of 20 percent over last year. For those who do initially stay home, more than two-thirds return to work despite still being contagious. That was the finding of the third annual Flu Season Survey from Staples.

It doesn't help that many workers are unaware of the different contagious periods for illnesses. The study revealed that 65 percent of employeesfeel it is only necessary to stay home between one and three days with the flu, when, in actuality, the flu virus can be contagious for one day before symptoms develop and up to seven days after becoming sick.

The top factor keeping employees from staying home sick is the need to get work done, even though a majority of workers said their average productivity level while ill was only around 50 percent.

The study points to dirty workplaces as one factor contributing to the ease of which germs are passed around the office. More than half of employeesclean their desks just once a week or less, even though germs can live on surfaces for up to three days.

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"We know that companies are already doing more with fewer resources, and flu season has the potential to impact productivity," said Lisa Hamblet, vice president for facility solutions at Staples Advantage, the business-to-business division of Staples. "Prevention is key."

The study was based on surveys of 150 office workers and 100 facility managers at organizations of all sizes across the U.S.

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