Across New York, nearly 66,500 people have tested positive for the coronavirus and 1,218 people have died, Gov. Andrew M. Cuomo said on Monday. Most cases are concentrated in New York City, where over 36,000 people have tested positive.

Sitting on a bench at the 170th Street station, Ms. Encanción stretched a medical mask across her face and slipped her hands into latex gloves. The risk of exposure to the coronavirus on the subway is just part of the simmering anxiety that hangs like a backdrop to her everyday life.

Her two teenage children are desperate to see their friends, but she only allows them to leave the family’s two-bedroom apartment for a walk with their aunt once a day.

Ms. Encanción’s husband was a janitor at a private school until he was laid off after the school shut down, slashing her family’s income in half. They have enough savings to cover this month’s rent, but nothing more.

“Next month how will we pay? I can’t even think about it,” she said.

Ms. Encanción was one of the few passengers on her line on a recent weekday after ridership across the subway plunged nearly 90 percent compared with the same day last year, according to the Metropolitan Transportation Authority, which runs the subway and buses.

Put differently, before the crisis erupted more than five million people squeezed onto the system every day — today, it carries fewer than 1 million.

But a Times analysis of M.T.A. data shows that ridership declines in each of the four boroughs served by the subway vary significantly and largely along socioeconomic lines.