New York City mayor Bill de Blasio announced on Wednesday that the city will close public schools in order to combat the rising COVID-19 numbers.

The Associated Press reports that all school buildings will be closed for in-person learning "until further notice." All students will be taught online only for the time being, although as of October only 25 percent or so of students had returned to in-person learning. Officials had expected more would return when elementary schools in the city reopened on Sept. 29, and high schools on Oct. 1.

In a tweet, Blasio noted that the city had "reached the 3% testing positivity 7-day threshold," which resulted in the closure decision. "We must fight back the second wave of COVID-19," he added. When schools opened around late September, the seven-day positive test average rate was under 2 percent.

Department of Education Chancellor Richard Carranza stressed in a letter to parents that this is a "temporary closure" and schools will "reopen as soon as it is safe to do so."

Despite reopening just a few months ago, a number of schools have had to go through temporary closures after students and/or staff tested positive. When high schools opened again, de Blasio called it "an absolutely amazing moment," He added, "We did something that other cities around this country could only dream of, because we have fought back this pandemic so well for so long." 

There's been over 574,000 confirmed cases of the virus in the state of New York since the start of the pandemic, with 290,000 of those in NYC. Cases have been steadily rising in the state since late September, with a steady increase in daily new cases since the start of November.