Forty-five percent of those surveyed said they work while sick because they can’t afford to lose the money — a phenomenon Ziebarth and his co-author call “contagious presenteeism.” Sick people come to work and infect their co-workers, spreading disease. Sick parents without paid leave are also more likely to send their sick kids to school to infect other children.

“The specific occupations that need it the most, don’t have sick leave,” Jeff Hayes, study director at the Institute for Women’s Policy Research, told HuffPost. “It’s people that are right in your face when they’re doing their job,” said Hayes.

The movement for paid sick leave has been gaining momentum since San Francisco passed a paid sick leave law in 2007. Several other cities and states have followed, including Washington, D.C., Seattle, Philadelphia and New York City. Connecticut was the first to pass a statewide law in 2012. California, Massachusetts and Oregon followed in 2015, and more localities are expected to come on board in the next few years. Large employers are also starting to reconsider stingy policies.

Typically, most workers wind up using three paid sick days a year, said Hayes, who follows the studies on paid leave. “There are very few jobs out there that can’t be put off for a day or two,” he said.