The barista who made your latte might have a cough. The cashier handing you your change might have the sniffles. The bus driver, with whom you share the same air for your 30 minute bus ride, might have the flu. Unless you live in San Fransisco, Washington DC, or Connecticut, all of the above are more than possible on a day to day basis. And it's all because paid sick-leave is not mandatory in most of the country.