(CNN)Major League Baseball has made several strict changes to its health and safety protocols in the wake of recent Covid-19 outbreaks, according to a league memo.
The memo, which was sent to clubs Wednesday, cites the Miami Marlins' outbreak.
"MLB investigators have now conducted a thorough investigation of the factors contributing to the spread of the virus within the Marlins traveling party, and our decision to revise the protocols ... is based on many of the things that we learned," the memo states.
The changes include reducing the size of traveling parties, requiring staff members and players to wear face coverings while on the road and prohibiting players and staff to meet in hotel rooms without special permission.
Coronavirus-related postponements started after 21 members in the Marlin's organization, including 18 players, tested positive for the virus. The Philadelphia Phillies have also had several positive tests.
And earlier this week, an outbreak among Cardinals' players and staff raised further questions about MLB's plans to safely hold the season amid the pandemic.
Commissioner Rob Manfred warned union leader Tony Clark in a call last week that if the league and players don't do a better job of following Covid-19 protocols and managing the virus, Manfred could shut down the shortened season, ESPN reported.
CNN has obtained a copy of the memo. It closes by saying: "We recognize that these changes place additional burdens and restrictions on players and staff. But if we desire to play, they are necessary to limit infections and, if someone does test positive, to keep the virus from spreading. The behavior of every Covered Individual affects the players and staff on his or her team, and on other Clubs as well. Everyone must be accountable for their own conduct because the careless or reckless actions of a few can impact the health and wellbeing of everyone."
The changes are effective immediately
-- "Clubs must reduce the size of their traveling parties to only personnel who are absolutely essential to playing games."Those traveling on road trips should serve an essential function. When large numbers of people are traveling, at least four buses will be provided to ensure there's a physical distance between passengers. Clubs should also ensure there's distance between those traveling on airplanes and not seat more than two people in a row.
-- "All staff and players must wear face coverings at all times in the hotel on the road (except when alone in their rooms), and at all times when in public places while traveling on the road.
Surgical face masks or N95/KN95 respirators should be used on buses and airplanes.
-- "While we are not at this time banning eating and drinking on planes, players and staff must be mindful of limiting the amount of time they remove their masks for purposes of eating and drinking."