"For the first time in months, you will see a daily number over three percent. Obviously, everyone is concerned about that," Mayor Bill de Blasio said.
New York City reported a coronavirus daily positivity rate of 3.25% and a 7-day average of 1.38%.
Mayor de Blasio said that the city will keep schools open or closed based on the 7-day average, not the daily number.
About 300,000 public elementary school students returned to classrooms Tuesday. Middle and high school students report by the end of the week. About half of all public school families opted into in-person learning and the other half opted to keep kids home for remote learning.
He noted that nine zip codes are experiencing most of the increases "The daily number is much affected by the challenges we are seeing in those nine zip codes," the mayor said.
"We are deeply concerned about the alarming increase in COVID-19 in the zip codes in Brooklyn and Queens," NYC Health Commissioner Dave Chokshi said.
In order to keep the numbers down, Mayor de Blasio said that anyone spotted not wearing a mask will be offered one and reminded that it is required, and if they refuse, they will be fined. He said "aggressive" enforcement on that is now underway.
On Monday, the mayor said the hospital admitted 71 new patients, the threshold is 200. For new cases on a 7-day average the city was up to 338 out of a threshold of 500. The daily positivity number was at 3.25% with a threshold of 5%.
Taking a deeper dive into the numbers and areas seeing an uptick in COVID-19 cases, the mayor said the neighborhoods make up 25% of all positive cases in the city.
- Gravesend/Homecrest 11223, 6.92%
- Midwood 11230, 5.64%
- Kew Gardens 11415, 3.31%
- Edgemere/Far Rockaway 11691, 4.91%
- Borough Park 11219, 6.23%
- Bensonhurst/Mapleton 11204, 6.05%
- Gerritsen Beach/Homecrest/Sheepshead Bay 11229, 4.05%
- Flatlands/Midwood 11210, 4.73%
- Kew Gardens Hills/Pomonok 11367, 3.04%
The city says they are also watching:
- Rego Park 11374, 2.64%
- Kensington/Windsor Terrace 11218, 2.72%
- Brighton Beach/Manhattan Beach/Sheepshead Bay 11235, 2.85%
If enforcement efforts with social distancing and mask wearing don't work, the mayor said there will be more stringent measures taken, including closing down non-essential businesses and banning public gatherings larger than 10 people.
"No one wants that to happen if it can be avoided," de Blasio said.
RELATED: Stay informed with ABC7's NYC COVID-19 positivity rate tracker
WATCH: Eyewitness to a Pandemic
MORE CORONAVIRUS COVID-19 COVERAGE
How coronavirus changed the New York region
Do you have coronavirus symptoms?
What's Open, What's Closed in the Tri-State area
Back to school information
COVID-19 Help, Information. Stimulus and Business Updates
New York City
Westchester and Hudson Valley
abc7NY Phase Tracker: