Originally Published: 14 DEC 21 00:11 ET

Updated: 14 DEC 21 08:48 ET

By Steve Almasy, CNN

(CNN) -- With winter almost upon us and people spending more time indoors, Covid-19 cases have been rising.

Sports groups and their players have not been spared -- and Monday saw several announcements connected to the protocols each league has set up for competitors and staff members.

Here's a look at the Covid news from the NBA, NHL and NFL:

NBA postpones first games

With 10 players and additional staff members in the NBA's health and safety protocols, the league has postponed the Chicago Bulls' two upcoming games.

This is the first time this season that NBA games have been postponed because of Covid-19 concerns.

Players in the protocol must quarantine for 10 days or have two negative tests in a 24-hour period.

The Bulls were to play host to the Detroit Pistons on Tuesday and then travel to Toronto to face the Raptors on Thursday.

Tickets for Tuesday's game will be valid for the game when it is rescheduled, team officials said.

No makeup dates were announced.

A league source told CNN last week that 97% of NBA players are vaccinated, with 60% of eligible players having received a booster shot. There are about 500 players across 30 rosters.

No major professional sports league in the United States has required its players to be vaccinated.

While the Bulls are the first team to have games moved, several star players have had to sit out while on the protocol list, including LeBron James, who missed a game late last month.

NHL see third team affected

The Calgary Flames have postponed at least their next three games after the NHL announced Monday six players and one staff member have entered the league's Covid protocol within a 24-hour period.

NHL officials said there is concern about the virus' continued spread throughout the team by warning of the "likelihood of additional positive cases in the coming days."

On Monday morning, the Flames, who are second in the Pacific Division, announced Elias Lindholm, Andrew Mangiapane, Brad Richardson, Adam Ruzicka, Chris Tanev and Nikita Zadorov were the six players who entered protocol.

This is the third time this season an NHL team has been forced to abruptly halt its season due to an outbreak within a team. The Ottawa Senators announced on November 15 that they would shut down their training facility and postpone three games when at least 10 players entered the NHL's Covid-19 protocol.

Later in November, the New York Islanders had two games postponed due to multiple players in Covid protocol.

The Flames facilities have been indefinitely closed. The impacted games have yet to be rescheduled.

NFL wants staff boosted by after Christmas

In the NFL, where a Covid-19 outbreak could lead to a forfeit, the league sent a memo Monday that Tier 1 and Tier 2 staff who have previously been vaccinated and are eligible under CDC guidelines must receive a booster shot no later than December 27.

Tier 1 and Tier 2 staff are coaches and anyone that has direct contact with players. This mandate does not apply to NFL players.

A league source told CNN that there were 37 positive coronavirus tests from players. ESPN's Adam Schefter was first to report that figure.

The most recent publicly released testing data from the NFL showed 29 positive tests from players between November 14-27.

On December 2, the league stated that 94.4% of its players were vaccinated along with "nearly 100%" of other personnel.

Heading into their high-profile clash with the Arizona Cardinals on Monday Night Football, the Los Angeles Rams had placed five players on the Reserve/Covid-19 list, including starting cornerback Jalen Ramsey and starting tight end Tyler Higbee.

Earlier this month the NFL suspended three players, including Tampa Bay Buccaneers wide receiver Antonio Brown, for three games without pay following a league investigation that determined they violated Covid-19 protocols.

The NFL said its review of allegations that the players had "misrepresented their vaccination status" had supported the claims.