WELLNESS
12/24/2014 10:43 am ET Updated Dec 26, 2014

What The NHL Mumps Outbreak Teaches Us About Immunity

Mike Ehrmann via Getty Images

The unprecedented outbreak of mumps -- a contagious and occasionally dangerous virus -- in a professional sports league, the NHL, has led to player quarantines, cancelled events and, most recently, movement among NBA clubs that often share facilities to distance themselves from arenas and practice facilities also used by hockey players. The NFL, though its players don't have contact with hockey teams, has taken note as well, according to an ESPN report -- they know it could happen in their league, too.

Although the first mumps alert in the NHL -- from the Anaheim Ducks -- happened in mid-September, and the first official diagnosis occurred in mid-October, according to an ESPN timeline of player illnesses and absences, the outbreak's profile was raised significantly after star player Sidney Crosby of the Pittsburgh Penguins was diagnosed on Dec. 14. More recently, on Dec. 19, Crosby's teammate Olli Määttä tested positive for the virus. All told, 18 players have been diagnosed with the illness, while several others have missed games due to "mumps-like symptoms." The outbreak is not yet contained, and the league is bracing itself for additional illness.

Mumps is characterized by fever, fatigue, headache, muscle aches and a loss of appetite. This can be followed by swelling of salivary glands. About 20 percent of virus carriers will experience no symptoms at all. There is no recommended treatment beyond managing hydration levels and resting; most patients recover within about two weeks, according to the Mayo Clinic.

Experts say that professional sports teams are a breeding ground for this type of infection because the players are in such close contact during play, practice and travel. What's more, players from around the globe may have varying levels of immunity, based on differing vaccination requirements abroad. But even if all players were fully immunized against the highly contagious mumps, the vaccination for the virus is weak -- protecting only about 78 percent of those who get it. A booster shot bumps that up to 88 percent, though the booster wasn't common in the U.S. or Canada until the mid-90s, making any player over the age of, say, 30 less likely to have the higher immunity.

We spoke to Paul Offit, M.D., chief of the division of infectious diseases at Children's Hospital of Philadelphia (and a Flyers fan, for the record) about immunity, Mumps virus and what we can take away from this outbreak:

How did this happen?

Mumps is a highly contagious disease, spread by respiratory droplet. You can transmit it from coughing, sneezing, talking near someone.

When you start to have an erosion in herd immunity -- meaning a critical number of people in the community don't get vaccinated -- the most contagious virus will come first, because those are the viruses that require the highest level of immunity in a population to keep from spreading.

Why is herd immunity weak in this case? Don't we all get vaccinated against mumps?

Mumps is included in the MMR vaccine, but of the three -- measles, mumps, rubella -- it's the weakest.

Mumps vaccine was first approved for use in the U.S. in 1967 in a single dose, but doctors discovered that immunity would fade, so in the early 1990s, a second dose became routine. Even then, it may not be enough for lifelong immunity. The second dose is administered in early adolescence, so about 10 years later, in late adolescents, you can see some outbreaks. For example, college campuses have outbreaks -- my son went to University of Richmond, where there was an outbreak last year, and Ohio State University had one recently. The hockey league, obviously, is another collection of people in their late teens who spend a lot of time together.

So it's partly because of vaccination rates and partly because it's just the weakest of the three.

Would you say the anti-vaccination movement played a role in the low immunization rates in this case?

Maybe. It's hard to un-scare people, and it's easy to scare them. A significant number of people buy into some vague notion that vaccines cause disorders like autism. [Andrew] Wakefield's "study" did give this notion a boost -- he tied this feared common disorder for which there wasn't a known cause to vaccines. No matter how many studies you do to show it's wrong, people have a belief.

And it's understandable -- we ask citizens to get vaccines for 14 illnesses, as many as 20 inoculations in childhood, as many as five shots at a time for illnesses. They involve needles, they involve unseen diseases and serums that the average person doesn't understand.

It's similar to the 2010 whooping cough outbreak in that it could happen because we have a generation of parents who were not scared of the disease. You didn't have to convince my parents to vaccinate their kids -- they saw teens die of [things like] diphtheria.

So are we destined to withstand mumps outbreaks unless we can find a more effective vaccination? What can we do about the disease?

First of all, realize that before immunizations for mumps, there were three to four million cases per year. It was a common cause of sterility. We've virtually eliminated that. There are as many as hundreds of cases a year, but because those awful side effects were rare, we don't see them in the kind of numbers we used to.

Aside from that, make sure that people in outbreak situation get vaccinated with a booster dose. If you've had two doses, get a third dose.

And if you're sick, isolate yourself from others. And please don't visit the local hospital on a holiday visit, as I heard one player accidentally did while infected.

This interviewed has been edited and condensed for clarity.

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