Later, Mayor Mike Duggan said all of the city’s front-line employees, including bus drivers, would get $800 a month in hazard pay. He also announced that masks would be made available to riders on all buses.

But on the first day of the mask initiative last week, there were no masks on board the No. 17 bus Rochell Brown was driving.

A manager told her that riders were not required to wear them.

Ms. Brown, 49, shook her head and thought about a colleague who died this month from complications of Covid-19, the disease caused by the coronavirus. “It should be mandatory,” she said of the masks.

She saw herself at risk of a similar fate. She had a heart attack two years ago and has hypertension. The night before this ride, her doctor suggested she take time off for her safety.

Yet here she was, on a sun-soaked, mild spring morning, performing an “essential” duty for $19.13 an hour, but without, she felt, the praise and appreciation that police officers and emergency medical workers received. No one was peering out of a window clapping for her. Her bus was not even equipped with masks.