...(T)he virus can be passed to another individual before any symptoms occur. Players sharing water bottles, for example, wouldn't know they are spreading the virus. "That's probably how it's moving around between teams and within the teams," said Dr. Peter Lin, CBC’s medical columnist.

Sports teams are in close proximity in the locker room, and it becomes an easy setting for disease transmission. "The NHL is like any enclosed population — like dorms or schools. These are people that are in close contact with one another for long periods of time, and they are the ones most at risk for getting any infections," (says)...Dr. Todd Hatchette, chief of service for microbiology at Capital District Health Authority in Halifax.

...The MMR vaccine (for measles, mumps and rubella viruses) immunizes against mumps. The first shot is 70-80 per cent effective and the second shot boosts the effectiveness of the vaccine to 90 per cent.

Enforcing the use of hand sanitizers and making sure each player has his own water bottle are also ways for the NHL to try to control the outbreak...Health-care professionals recommend cleaning frequently touched surfaces regularly, not sharing drinks or eating utensils, and not touching your hands to your mouth.