Nearly all the buildings remained open, though six were closed temporarily, in accordance with city guidelines that only those schools that report at least two cases in different classrooms will be shut.
The cases occurred between Sept. 8, when teachers and staff members reported to schools, and Monday, when the first students entered classrooms.
In dozens of cases, the infected individuals got the positive test results and did not report to work, the department said. Others did report to school, and their close contacts in the buildings were told to quarantine for two weeks.
Avery Cohen, a spokeswoman for Mayor Bill de Blasio, said that the cases included a “handful” of students, but that “the vast majority were among staff before schools reopened for students.”
Some public health experts said the statistics reflect a new reality.
With in-person learning taking place in a system with 1.1 million schoolchildren, 75,000 teachers, and 2,500 school buildings and early childhood centers, new cases will most likely be a daily occurrence, they said. Individual building closings will also be common, they said.
Dr. Michael Mina, an assistant professor of epidemiology at the Harvard T.H. Chan School of Public Health, said New York City families should be prepared for a constant game of Whac-a-Mole. The virus is likely to re-emerge repeatedly in school buildings until there is either a vaccine or very frequent testing, he said.
Ideally, Dr. Mina said, 50 percent of all students and staff members should be tested three times a week.