NHL officials believe that protocols put in place after a widespread mumps outbreak within the league two seasons ago have helped curtail a return of the highly contagious virus this season.
Zach Parise and Jason Pominville of the Minnesota Wild -- who were diagnosed with the mumps on Feb. 27 and subsequently quarantined -- returned to action on Sunday night and each contributed a point during Minnesota's win over the San Jose Sharks. Several Vancouver Canucks players also showed symptoms of the mumps several weeks ago, but the team has controlled the spread of the virus as well.
All Canucks players who had confirmed cases of mumps are beyond the contagious stage, the team reported on Monday, and three of the four players who had mumps are back in the lineup. An assistant trainer was also diagnosed with the virus, while two other Vancouver players were tested, but the tests came back negative.
Sources from both the Nation Hockey League Players' Association and the league told ESPN.com that they are confident this outbreak has been contained and that the league won't have to deal with the anxiety they experienced during the 2014-15 season, when about two dozen players -- including Pittsburgh Penguins star Sidney Crosby -- on at least five teams and several on-ice officials were diagnosed with the virus.
Hockey certainly presents a hospitable breeding ground for the virus -- which is found in saliva and respiratory droplets and is spread person to person through coughing, sneezing or coming into contact with saliva -- given the close quarters players share on and off the ice and the potential for the airborne disease to infect players on different teams in different geographic regions.
It's also clear there has been an uptick in the number of cases of mumps reported in the United States as a whole. In 2016, 5,311 cases of mumps were reported, the highest in a decade, the Center for Disease Control told ESPN.com.
"CDC is investigating the factors that may have contributed to the increase in cases, including that the vaccine prevents many but not all cases of mumps, the disease spreads more easily in crowded settings, and the possibility that the protective effect of the vaccine decreases over time," Ian Branam, a press officer with the CDC's National Center for Immunization and Respiratory Diseases, wrote in an email.
Branam did not have any data about whether hockey teams are more likely to contract mumps than other sports, although it's worth noting that vaccinations aren't guaranteed to stop the virus and that "outbreaks have still occurred in highly vaccinated communities, particularly in close-contact settings," said Branam. "Crowded settings like college campuses, schools, and sports teams are more likely to have outbreaks."
The fact that the recurrence of the disease in the NHL seems to have been brought under control quickly and with minimal spread suggests that the league learned from the outbreak two years ago.
For instance, the league and players' union recently sent a memo to all teams reminding players of the importance of having two documented vaccines against mumps, or the Measles Mumps Rubella (MMR) vaccine. If players were unsure if they had two of the shots, they were advised to get another as a safeguard.
Those players who were exposed to the virus were also advised to get another dose of the vaccine regardless of whether they'd already had the two initial shots, according to players' association officials.
The ongoing educational component in safeguarding against the mumps is important, given the number of young players who've joined the league since the previous outbreak. Teams and players were reminded not to share towels or water bottles and to frequently wash their hands. Teams were reminded that they should continue to use disinfecting techniques for equipment aimed at controlling the spread of communicable disease, as well as general disinfecting of common areas like the locker room.
In 2014, the NHL/NHLPA joint infection control subcommittee put protocols in place to try to limit the transmission of the disease between teams, including providing new towels for the bench and in penalty boxes at the start of each period that were intended for a single use. Water bottles were disinfected after each use and players were advised not to put their mouths directly on the bottles.Those protocols remain in place.
Both the Wild and Canucks worked with the league and players' association, and with state/provincial medical officials, to contain the spread of the disease by quarantining players and/or staff who'd been exposed to the disease.