Students in Passaic City and Camden City public schools will be masking up against COVID-19 and other respiratory viruses in the new year.

The two districts announced they would each temporarily return to mask mandates for students, staff and visitors last week.

“When Passaic County is in the moderate or below range, the mask mandate will be lifted,” Passaic Public Schools Superintendent Sandra Diodonet wrote in a Dec. 20 letter to parents and guardians. A day later, the Camden City School District announced its own mask mandate, which will be in effect for the first two weeks of the spring term.

The change affects about 20,000 enrolled students and 1,700 classroom teachers across the two districts, according to data from the National Center for Education Statistics.

Other schools and districts are emphasizing testing over masks. Fred W. Martin Center for the Arts P.S. 41 in Jersey City distributed at-home tests to students before the break, according to a letter sent to parents on Dec. 20.

“Masks are an option for any student or staff member concerned with airborne illnesses such as COVID-19 and the flu,” the letter says.

The news comes as confirmed COVID cases continue to rise across the state, driven by the highly contagious BQ.1 and BQ.1.1 variants. As of the state’s most recent COVID-19 Weekly Activity Report, issued Dec. 22, all but three New Jersey counties were considered high-transmission by the Centers for Disease Control and Prevention.

Confirmed school cases have been rising steadily throughout December, according to the state Department of Health’s tracking. For every 1,000 students, there were 2.81 known coronavirus infections the week ending Dec. 18 — up from 1.4 students about a month earlier on Nov. 20. Staff rates in that time had nearly doubled, to 8.10 infections per 10,000 staff members. But just under half of New Jersey schools are included in this data; the rest didn’t submit their COVID numbers in time to be included. Last week, NJ.com reported districts vary widely in their COVID data reporting conventions, making it hard to discern where transmission is highest.

Cases and hospitalizations have ticked up in many counties, but there are still ample beds at local hospitals, according to the state health department. Nevertheless, at this level, the agency recommends universal indoor masking, as well as special precautions for people at higher risk of severe disease.

The state is also seeing ongoing outbreaks of influenza and respiratory syncytial virus, also known as RSV, which, along with COVID, threatened to overwhelm New Jersey hospitals earlier in the season.

The “tripledemic” pushed health officials in nearby New York City to recommend, but not require, universal masking earlier this month. Philadelphia public schools, meanwhile, announced their own short-term January mask mandate in mid-December.

It’s unclear how other large school districts will manage COVID, flu and RSV transmission after students return from winter break.

Last winter, skyrocketing COVID cases prompted hundreds of schools to adjust schedules, switch back to virtual learning or offer hybrid options for the first few weeks of the school year. New Jersey dropped its statewide school mask mandate in March, but some districts kept their own for the duration of the 2021-2022 school year.

Christi Peace, deputy press secretary for Gov. Phil Murphy, said state government isn’t planning to reinstate an across-the-board school mask mandate.

“Districts can continue to make that decision at the district-level in collaboration with their local health officials,” she said in a written statement. “Individuals can decide whether to wear a mask, themselves, if no requirement is in place.”

Peace also stressed the importance of getting COVID and flu vaccines and boosters, practicing handwashing and keeping sick kids home from school.