At least five NHL teams have reported 15 players who have contracted the mumps virus. The most high profile is Pittsburgh Penguins captain Sidney Crosby, captured in photographs with one swollen cheek. Late Tuesday, the Penguins confirmed forward Beau Bennett is also infected.
Teams have been scrambling to get their players revaccinated against the virus. It's a smart move; mumps outbreaks can last for months if the virus gets into a group of susceptible people.
"Given that they're going to continue to be exposed to each other with their very busy schedule, this could fester for a while," Dr. Greg Wallace, a mumps expert from the U.S. Centers for Disease Control, said Tuesday of the NHL outbreak.
Vaccinating NHL teams should help to shorten the length of this outbreak. But it takes several weeks for the vaccine to generate a good antibody response, and the vaccine doesn't protect in 100 per cent of cases.
As well, the incubation period of the disease is long — 12 to 25 days. So there could be players now who are infected but unaware of that fact, meaning more players could be sidelined with mumps over the next three weeks.
The mumps virus can cause inflammation in the salivary glands found in the cheek, under the tongue or under the jawbone, leading to the characteristic facial swelling. Both sides of the face can be affected, but it isn't uncommon to see only one side puff up.
The once common viral disease infected most people in childhood before a mumps vaccine was introduced in the early 1970s.
The use of vaccine has reduced the number of mumps cases in Canada by about 99 per cent, said Dr. Gaston De Serres, an infectious diseases expert with Quebec's provincial public health agency.
But sporadic outbreaks continue to be recorded. A large epidemic occurred in 2006 and 2007; the outbreak, which began in Nova Scotia, eventually stretched to all 10 provinces, though several had fewer than two dozen cases. The total for that outbreak was 1,284, 777 of them in Nova Scotia.
Contemporary outbreaks often happen in groups of people who have close interactions. University campuses have been the site or source of many outbreaks in recent years, said Dr. Bonnie Henry, British Columbia's deputy provincial health officer.
The virus is spread through saliva droplets, so activities like kissing or sharing a cigarette or marijuana joint can propel the virus through groups of students, she said.
It's easy to see the opportunities for spread among hockey players. In fact, Dr. Shelley Deeks of Public Health Ontario agreed hockey provides a perfect scenario for spread of the mumps virus.
There are the cramped quarters on the bench and in the locker-room. The shared water bottles. Players coughing or gasping to recover their breath after the exertion of a breakaway or a busy shift. The nose-to-nose jostling that can be the foreplay of a fight.
"You've got this group of people who are relatively susceptible given their age and then you introduce a virus into that population," said Deeks, who is the Ontario agency's medical director for immunization and vaccine preventable disease.
But why are the NHLers relatively susceptible? After all, they are of an age where they were likely vaccinated against mumps in childhood. And any — like Crosby — who played in the Sochi Olympics earlier this year were likely given a booster dose of measles, mumps and rubella vaccine — though the concern heading to Sochi was measles, not mumps.
Anyone born before 1970 is assumed to have had mumps in childhood because the virus circulated routinely then. And even those born between 1970 and 1980 are thought to have pretty good protection. They would have received a dose of vaccine, but they may too have gotten the mumps — the virus still circulated during that time.
After 1980, though, mumps became rarer as the effect of vaccination programs took hold, Deeks explained.
But in the early days of mumps vaccination, it was thought one dose would suffice to immunize children for life. Later it became apparent that wasn't true and a two-dose regimen was adopted in Canada around 1997, Henry said.
Even at two doses, the mumps vaccine is not the most effective vaccine on the market. During a 2011 outbreak in British Columbia, about five per cent of the 132 cases were people who had received two doses of vaccine.
"It's not a perfect vaccine. And there are some people who will have two doses and will still get sick with it. If they've been exposed and they've had a high level of exposure, then they may not have enough antibody to protect them," Henry said.
Wallace said two doses of mumps vaccine protect about 88 per cent of people from the mumps virus. "So it's easy to imagine if you've got 100 players and staff who are basically constantly together during the season, that if they're all exposed you could potentially see 10, 12, 15 getting it."
But keep in mind today's hockey players are from the cohort that typically received only one vaccination. At one dose, the vaccine is thought to protect between 60 and 90 per cent of people, Henry said.
Containing a mumps outbreak can be tough. Wallace said an infected person is contagious a day or two before he or she shows symptoms of being ill. That means you can isolate a hockey player once you know he has mumps. But by then he may have already spread the virus to a teammate or an opponent.
Also, the severity of symptoms varies, with some people showing few or barely any symptoms. Wallace said it is not known if people with very mild mumps are as contagious as people with more severe symptoms.
In addition to the swelling of salivary glands, mumps can cause inflammation in the testicles in post-pubescent males, the breast tissue of pubescent girls and the ovaries of females past puberty, De Serres said.
Orchitis — the swelling of one or both testicles — happens in about one-third of mumps cases in adult males, he said.
Many people believe mumps that involve orchitis can lead to infertility. But that is rarely true. "It's something that people talk about, but its impact on fertility, it's not big," said Wallace.
In some cases, mumps can lead to permanent deafness — generally in one ear, on the side where swelling occurred. It can also trigger meningitis — inflammation of the membranes of the brain and spinal cord — and on rare occasions, encephalitis, which is inflammation of the brain.
But the complication rates tend to be lower among people who have been vaccinated.