The recent outbreak of mumps has emerged as one of the most bizarre yet compelling storylines of the 2014-15 NHL season.

Multiple teams have been affected, several players have been sidelined, and meanwhile, we are all left scratching our heads about what exactly it all means.

Unless you were permanently scarred from that fateful visit to the doctor's office as a child and have purged the memory entirely, you might recall the term "mumps" from your mumps-measles-rubella vaccination, also known as the MMR shot.

Mumps is a vaccine-preventable disease defined by symptoms such as fever, headaches, muscle pain, fatigue and swollen glands. It is a droplet respiratory disease spread person-to-person and generally from close, prolonged contact.

Given the close-knit nature of a locker room, it's not surprising to see mumps spread from teammate to teammate. Both Corey Perry and Francois Beauchemin of the Anaheim Ducks contracted mumps. The St. Louis Blues reportedly had incidences. Tanner Glass of the New York Rangers had a confirmed case, but the Minnesota Wild have been hit most significantly, with Ryan Suter, Keith Ballard, Marco Scandella, Jonas Brodin and Christian Folin all felled by the disease. And on Wednesday, the Bergen Record reported that both Travis Zajac and Adam Larsson of the New Jersey Devils have been diagnosed with the mumps.

Ryan Suter is one of five Wild players diagnosed with mumps this season. Brace Hemmelgarn/USA TODAY Sports

"We've had probably about five people impacted around our team out of about 50 people, so that's about one in 10, and we figured everybody was exposed to it," Wild general manager Chuck Fletcher told ESPN The Magazine's Craig Custance at this week's board of governor's meetings in Boca Raton, Florida. "Ten percent of our team population contracted it. As far as I know, everybody received the immunization when they were young. We were all immunized again a few weeks ago. It's been a tough process to go through. We've tried to take every precaution possible. It's been a very difficult thing to get on top of, [but] I think we've done the best we can. We seem to have one player get it, a week off, and another player get it. It's been frustrating that way."

When the outbreak began is difficult to pin down, although it could date back to the preseason. How the disease has spread to multiple teams within the NHL is hard to nail down as well.

Experts don't think a game situation would be the most efficient mode of transmission, but it can't be ruled it out either, given the type of contact that arises from fighting, hitting and battling opponents down low in front of the goal.

According to Dr. Greg Wallace, the lead of the domestic measles, mumps, rubella and polio team at the Centers for Disease Control and Prevention in Atlanta, Georgia, there have been anywhere from a couple hundred to a couple thousand cases reported annually over the past 15 years, and that's not counting the number of unreported cases that result when a person exhibits just mild symptoms or no symptoms at all.

Although the mumps vaccine's effectiveness is not nearly as high as others -- Wallace estimates it to be around 88 percent -- the disease is not as contagious as, say, measles. It's not easy to identify why some people exhibit symptoms and why others do not, Wallace said. It's also difficult to predict what impact the disease will have on a defined group.

"There are a couple of unique challenges with mumps. Part of that is the incubation [period] is long and can vary quite a bit -- 12 to 25 days," Wallace told ESPN.com "The other challenge is that some -- a relatively high proportion of those infected -- are going to show little or no symptoms, and we don't know how well they will spread [the disease] to others."

The current protocol for teams is to quarantine players for at least five days after they start exhibiting symptoms, though some clubs opt to err more on the side of caution (the Ducks kept Perry and Beauchemin away from the team for almost a week). An additional vaccine can be administered to boost immunity within the defined group, which several teams have done.

The Islanders, for example, administered mumps vaccines to not just the players but also the hockey operations crew and traveling team staffers.

"It's been a difficult process to go through. Part of the problem is, from what I understand, you're sometimes contagious three to four days before the symptoms appear," Fletcher told ESPN the Magazine. "It's very difficult in a dressing room environment to separate, to segregate the ill player because you may not know he's ill."

The Ducks kept Corey Perry and Francois Beauchemin away from the team for almost a week when they had mumps. Tim Heitman/USA TODAY Sports

Meanwhile, the NHL is trying to disseminate as much information as possible on the subject so teams can be proactive about the issue.

According to a league spokesperson, in November, "comprehensive instructions," including links to the CDC website and "assorted literature" regarding mumps, were sent to team physicians and head trainers on behalf of the league's infection control subcommittee.

The league made the same recommendations that it does for cases of the flu, and vaccination decisions were left to each team's medical staff and players. A player cannot be forced to receive a vaccination.

The players union has also been working to keep its constituents informed of the developments.

"The NHLPA has been actively educating the players regarding the recent outbreak, while providing best practices on how to avoid contracting and spreading mumps," a union spokesperson told ESPN.com via email.

Wallace said he has known of a college lacrosse team and participants of a rugby tournament experiencing a mumps outbreak, but he has never before seen a threat to an entire professional sports league.

Spokespeople for the NFL, MLB and NBA each told ESPN.com via email that their respective leagues had not received any reports of cases.

Tim Frank, senior vice president of basketball communications for the NBA, is monitoring the situation, however, and providing information accordingly.

"Last week, we sent a memo out to our teams to convey information from the CDC with a reminder to review the immunization history of players and any other individuals under the care of the team medical staff," Frank wrote in an email to ESPN.com.

Perhaps the biggest question facing the NHL is whether the problem is anticipated to get worse or taper off. With the lengthy incubation period and unknown variables that define mumps, it might be months before we know.

"The way we define the end of an outbreak is if we find no cases in a group [we're] concerned about for two full incubation periods," Wallace said. "It's hard to predict how long this can fester on or how quickly it can burn out."

That means 50 days from the point of the last reported case. Essentially, don't expect any quick resolution to this issue. What has been one of the more baffling developments of the season might continue to be a concern.