The outbreak of the mumps in the NHL is unprecedented in professional sports, but it isn't all that unusual in the everyday world. Here's what we know about the virus, which NHL players have been diagnosed or suspected of being diagnosed with it, and the chain of events surrounding the spread of the virus.

What we know about the mumps:
• From the Centers of Disease Control and Prevention website: "Mumps is a contagious disease that is caused by the mumps virus. Mumps typically starts with a few days of fever, headache, muscle aches, tiredness, and loss of appetite, and is followed by swelling of salivary glands."

• Since 1967, Americans are immunized against mumps, measles and rubella around 12 to 15 months old and again before kindergarten; before the vaccine was administered, 186,000 cases of mumps were reported every year.

• Since 1969, Canadians are immunized against mumps, measles and rubella around 12 to 15 months old and again either at 18 months or before kindergarten; in the early 1950s, there were more than 34,000 cases of mumps a year.

• A booster shot is recommended for those born after 1970 and for those who travel outside of North America.

• Vaccines protect 78 percent of people.

• Immunity from mumps dissipates over time.

• People born between 1970 and 1992 have partial protection against the virus because they received the standard single shot; a booster shot was not standard procedure until the mid-1990s

• Two shots are effective 88 percent of the time.

• Once you have had full-blown mumps, you are immune for the rest of your life.

• Spreading of the virus can be prevented through use of hand sanitizers and by avoiding sharing certain items, such as water bottles.

• There is a 12- to 30-day incubation period.

• One in 5 people with the virus never show signs of symptoms.

• The virus is spread through saliva and mucus by coughing and sneezing, especially in close quarters, such as in dressing rooms, schools and dorms.

• Symptoms are displayed 12-25 days after infection.

• There is no treatment for the virus; it is "self-limiting."

• The virus generally takes 7-10 days to run its course; rest and hydration are the best ways to deal with the virus.

• Generally, the virus does not cause permanent damage; but in rare and extreme cases, it can cause sterility in men, brain swelling and deafness.

• There were 438 confirmed cases of the mumps in the U.S. in 2013; 1,078 have been reported in 2014, through Nov. 29.

• There were four outbreaks this year at universities: Ohio State, Fordham, Wisconsin and Illinois.

Players, officials diagnosed with mumps or showing mumps-like symptoms:

Anaheim Ducks: Corey Perry (Canadian), Francois Beauchemin (Canadian), Clayton Stoner (Canadian), Emerson Etem (American).

Minnesota Wild: Ryan Suter (American), Keith Ballard (American), Marco Scandella (Canadian), Jonas Brodin (Swedish), Christian Folin (Swedish).

New Jersey Devils: Travis Zajac (Canadian), Adam Larsson (Swedish), Patrik Elias (Czech), Scott Clemmensen (American), Michael Ryder (Canadian).

New York Rangers: Tanner Glass (Canadian), Derick Brassard (Canadian), Joey Crabb (with AHL Hartford; American), Lee Stempniak (American).

Pittsburgh Penguins: Sidney Crosby (Canadian), Beau Bennett (American), Olli Maatta (Finnish), Steve Downie (Canadian), Thomas Greiss (German)

St. Louis Blues: suspected but not confirmed

NHL officials: Referee Eric Furlatt, linesman Steve Miller.

No confirmations of team support staff being diagnosed with the disease have been reported, although an intern with the Pittsburgh Penguins radio staff has been confirmed to have the virus.

Timeline of events related to the mumps outbreak in the NHL:

Sept. 12: Local health unit issues mumps alert in Orange County, California, where some Anaheim Ducks players live.

Oct. 2: Blues play Wild in preseason game.

Oct. 4: Blues play Wild in preseason game

Mid-October: St. Louis Blues players reportedly test positive for mumps -- Joakim Lindstrom and Jori Lehtera reportedly had mumps-like symptoms -- although the team has never confirmed this.

Oct. 16: Referee Eric Furlatt works Blues-Kings game.

Oct. 17: Keith Ballard of the Minnesota Wild misses game against Ducks with mumps-like symptoms; referee Eric Furlatt works game.

Oct. 19: Ducks play Blues.

Oct. 23: Linesman Steve Miller works Blues-Canucks game.

Oct. 27: Wild play Rangers.

Oct. 30: Ducks play Blues.

Early November: Furlatt misses games with mumps-like symptoms.

Nov. 3: Blues play Rangers.

Nov. 4: Wild play Penguins; Blues play Devils; linesman Steve Miller works Blues-Devils game.

Nov. 5: Corey Perry and Ryan Getzlaf of the Anaheim Ducks miss game vs. Islanders with flu-like symptoms.

Nov. 6: Blues play Devils.

Nov. 7: Ducks play Coyotes; Getzlaf returns, Perry sits out second consecutive game.

Nov. 8: Marco Scandella of the Minnesota Wild shows first signs of mumps-like symptoms, but plays 22:04 against Montreal Canadiens.

Nov. 9: Ducks play Canucks; Beauchemin misses game with the flu.

Nov. 11: Wild play Devils; linesman Steve Miller misses game, later reported to be because of mumps-like symptoms; Perry and Beauchemin diagnosed with mumps; Rangers play Penguins.

Nov. 13: Wild play Sabres; Jonas Brodin and Scandella of the Wild sit out with illnesses later suspected to be mumps.

Nov. 15: Rangers play Penguins.

Mid-November: Team physicians sent email by NHL-NHLPA joint health and safety committee with recommended changes to bench and dressing room behavior.

Nov. 23: Ducks play Coyotes; Clayton Stoner of the Ducks scratched with mumps-like symptoms.

Nov. 24-28: Penguins immunized and tested for mumps.

Nov. 28: Sidney Crosby of the Penguins treated for injury to right side of neck; Crosby is treated and tested for mumps; results are negative.

Nov. 28: Tanner Glass of the New York Rangers sent home from Philadelphia after showing flu-like symptoms.

Nov. 29: Wild play Blues; Glass diagnosed with mumps; Rangers get booster shots.

Dec. 2: Devils play Penguins.

Dec. 4: Ryan Suter of Minnesota Wild diagnosed with mumps.

Dec. 8: Rangers play Penguins; Crosby plays 18:56, his shortest time on ice in eight games.

Dec. 10: Travis Zajac and Adam Larsson of the New Jersey Devils diagnosed with mumps.

Dec. 10-11: Crosby tested again; no symptoms displayed and tests showed no indications of an infection.

Dec. 11: Penguins visit nearby children's hospital.

Dec. 12: Crosby, who had previously had a booster shot before the 2014 Olympics, held out as a precaution after face swells; spent time around teammates in dressing room; Crosby's DNA sent to CDC for further testing.

Dec. 14: Crosby and Derick Brassard of the New York Rangers diagnosed with mumps.

Dec. 15: Beau Bennett of the Pittsburgh Penguins tested for mumps; Detroit Red Wings offer mumps booster shots to players.

Dec. 16: Bennett diagnosed with mumps.

Dec. 17: Marc-Andre Fleury, Robert Bortuzzo and Olli Maatta of the Penguins tested for mumps as a precautionary measure.

Dec. 18: Fleury tests negative for the virus, backup goalie Thomas Greiss held out as a precaution; Rangers isolate Lee Stempniak while he is tested for the mumps; AHL Hartford Wolfpack forward Joey Crabb and head coach Ken Gernander tested for mumps; radio intern with the Pittsburgh Penguins confirmed to have case of the mumps

Dec. 19: Olli Maatta tests positive for mumps.

Dec. 22: Penguins Steve Downie, Brandon Sutter and Thomas Greiss sent home from Florida to be tested for mumps virus; Crabb and Stempniak test positive for the mumps

Dec. 26: Downie and Greiss diagnosed with mumps.

Dec. 27: Patrik Elias, Scott Clemmensen and Michael Ryder of the New Jersey Devils diagnosed with mumps.