Coronavirus updates: US state sees record rise in daily cases over last 2 weeks

New York City's daily rate of positive COVID-19 tests is above 3% "for the first time in months," Mayor Bill de Blasio warned Tuesday.

The mayor has threatened to close schools if the seven-day rolling average is 3% or higher citywide. While the daily positivity rate now stands at 3.25%, the seven-day average remains below the mark for school closures at 1.38%.

"Obviously, everyone is concerned about that," de Blasio told reporters. "We have to be on high alert to make sure we fight back this challenge."

De Blasio said nine neighborhoods of Brooklyn and Queens are to blame for the uptick in cases. He also announced unspecified fines for anyone who refuses to wear a face covering, starting Tuesday.

"This is an inflection point," he told reporters. "We have to take more action at this point and more serious action and we will be escalating with each day depending on what we see happening on the ground and the test results we are getting."

The surge comes as hundreds of thousands of public elementary school students returned to classrooms across New York City on Tuesday for the first time in six months. Middle and high schools open later this week. About half of all families with children in New York City's public school system opted for in-person classes, while the other half chose to keep kids home for remote learning.

ABC News' Aaron Katersky contributed to this report.

An ABC News analysis of COVID-19 trends across all 50 U.S. states as well as Washington, D.C. and Puerto Rico found there were increases in newly confirmed cases over the past two weeks in 32 states plus Puerto Rico.

The analysis also found increases in the daily positivity rate of COVID-19 tests in 20 states, increases in COVID-19 hospitalizations in 21 states and increases in daily COVID-19 death tolls in nine states.

The trends were all analyzed from data collected and published by the COVID Tracking Project over the past two weeks, using the linear regression trend line of the seven-day moving average.

One state -- Kansas -- saw a record rise in the daily number of new cases, while two states -- Missouri and North Dakota -- hit a record number of current COVID-19 hospitalizations.

The White House coronavirus task force's latest weekly briefing for governors, obtained ABC News on Monday night, identified 22 states as currently in the "red zone" for COVID-19 cases, indicating more than 100 new cases per 100,000 population last week. There were 18 states in the "red zone" in last week's briefing and 15 states in the one prior.

ABC News' Benjamin Bell, Brian Hartman, Soorin Kim, Josh Margolin and Arielle Mitropolous contributed to this report.

The National Football League announced Tuesday that three players for the Tennessee Titans have tested positive for COVID-19 along with five of the team's non-player personnel.

As a result, the Titans will suspend in-person club activities starting Tuesday. The Minnesota Vikings, who played the Titans on Sunday, will also suspend in-person club activities.

"Both clubs are working closely with the NFL and the NFLPA, including our infectious disease experts, to evaluate close contacts, perform additional testing and monitor developments," the NFL said in a statement Tuesday. "All decisions will be made with health and safety as our primary consideration. We will continue to share updates as more information becomes available."

A dozen crew members on a cruise ship docked off the coast of Greece have now tested negative for COVID-19 twice after initially testing positive, according to the ship's operator TUI cruises.

The 12 crew members aboard the Mein Shiff 6 cruise liner tested positive for the virus on Monday and were immediately isolated, along with 24 other crew members who had come into contact with them. But those "unclear positive" results were later identified as negative by two further tests -- PCR (polymerase chain reaction) tests performed on the ship by TUI Cruises and rapid antigen tests conducted by Greek authorities in the port city of Piraeus, according to a press release from TUI Cruises.

"A further PCR test, carried out by Greek authorities, should confirm this again. The results are expected later today," the company said in the statement Tuesday, calling the incident a "possible false alarm."

None of the 12 crew members have shown any symptoms, and rapid antigen tests for the 24 close contacts also came back negative.

The ship departed Sunday night from the port city of Heraklion, the capital of the Greek island of Crete, with all 922 guests testing negative for COVID-19 prior to boarding. Crew members are tested for the virus every two weeks, according to a TUI spokesperson.

The company resumed cruise operations in late July in Germany and started sailing in Greece on Sept. 13, according to the spokesperson.

ABC News' Christine Theodorou contributed to this report.