The New York City subway has run round-the-clock since the day it opened in 1904. The subterranean mainstay, a symbol of the city’s tireless energy, has survived terrorist attacks, blackouts, and hurricanes. But since the COVID-19 pandemic began, ridership has plunged more than 90 percent and thousands of sick workers have hobbled the MTA’s ability to run service as officials scramble to disinfect the...