Some New York City public schools will have to shutter just days after they fully opened due to a spike in COVID-19 cases in certain neighborhoods.

On Sunday, Mayor Bill de Blasio revealed that he will “rewind” the reopening of schools in nine neighborhoods that have seen a testing positivity rate of over three percent in the last week, The New York Times reports.

“Today, unfortunately, is not a day for celebration,” Mr. de Blasio said. “Today is a more difficult day.”

Alongside public and private school closures, nonessential businesses and daycare centers will shutter as well. The virus has been spreading in areas in Brooklyn and Queens, which have large populations of Orthodox Jews. The nine neighborhoods in question are parts of Far Rockaway and Kew Gardens in Queens, and Borough Park, Midwood, Gravesend, Bensonhurst, and Sheepshead Bay in Brooklyn.

De Blasio is also curbing indoor dining and closing gyms and pools in 11 other neighborhoods that are also seeing rising rates of cases. These include parts of Williamsburg, Bedford-Stuyvesant, Fort Greene, Clinton Hill, Manhattan Beach, Bergen Beach, Kensington, and Crown Heights in Brooklyn. The Queens neighborhoods include Rego Park, Fresh Meadows, Hillcrest, and Jamaica Estates.

The mayor’s plan impacts 20 of the city’s 146 zip codes—and speaks to concerns of a second wave of the virus. If Gov. Andrew Cuomo approves the mayor’s proposal, then it would be enforced on Wednesday and would last two to four weeks, contingent on whether transmission can be contained.

A majority of the schools that will close are nonpublic yeshivas in Orthodox Jewish neighborhoods. Around 200 private schools will shutter and 100 public schools.

The mayor stressed the fact that the closures are “out of an abundance of caution” and not due to outbreaks. “We have seen very little coronavirus activity in our schools,” he added.

Houses of worship will still be open in the neighborhoods that are facing new restrictions.