The flu outbreak in Boston has employers on high alert, giving door knobs and elevator buttons an extra cleaning, holding additional flu clinics, even recommending that workers sprinkle sprouted garlic on their salads to boost their immune systems.

Boston has reported more than 750 confirmed cases of the flu this winter, up from just 70 last winter, prompting Mayor Thomas M. Menino to declare a public health emergency last week. The workplace is one of the main places where illness can spread like wildfire, in part due to the many people who drag themselves into the office when they are coughing, feverish, and achy.