Why is NHL facing unprecedented mumps outbreak?

Ice Hockey

More than a dozen NHL hockey players have reportedly been diagnosed with the mumps in recent weeks, prompting obvious questions about how and why the disease is spreading among the athletes.

(USA Today reports today that three more players have been added to the NHL’s list of mumps cases.)

We asked Steven Davis, M.D., the medical director of infection prevention at Baylor Medical Center at Irving, to weigh in on the mumps outbreak. Here’s what he wrote:

Mumps infection causes parotitis or swelling of the parotid gland that leads to the classic facial swelling that has been described in the hockey players. Mumps infection can also cause orchitis (testicle swelling), meningitis (brain inflammation) and swelling of other organs, like the pancreas.

Interestingly, older individuals can experience more severe manifestations of mumps, just as with some other viral diseases like chickenpox.

Mumps infection is caused by a virus that was common in early childhood before development of Measles, Mumps and Rubella (MMR) vaccine in the 1960’s. There was hope with MMR vaccination campaigns that these illnesses could be eliminated.  

The measles, mumps and rubella viruses are extremely infectious. Unfortunately, within the past decade or so several epidemics have been reported in young adults rather than children. Outbreaks have often occurred in the setting of individuals who live in close contact, like college dorms or, for that matter, NHL locker rooms. The incubation period is around 14 days, and persons remain infectious for about five days after the facial swelling begins.

Infections in recent epidemics have occurred even in persons who were previously vaccinated. This was especially true for persons who received one, rather than the recommended two MMR shots. Also, the infection was more common in persons who had completed the recommended two shot regimen of MMR more than 10 years ago. Further, persons who have not been immunized can serve as the “tinder that ignites the wildfire” of an outbreak amongst those with waning immunity from remote vaccination.

A distinct “genotype G virus,” found in recent outbreaks, is able to infect persons that may have waning immunity from remote vaccination with the present “genotype A-derived” vaccine. Rather than in elementary age children, as was often seen in the pre-vaccination era, these recent outbreaks have occurred in the college age and young adult setting.

In the outbreak setting, revaccination with a third dose of the MMR “genotype A” vaccine does stimulate immune response and reduce infection in these college and team exposures. Perhaps, future vaccine formulations or vaccine schedules will allow better control of the mumps “genotype G” virus infection as they occur now versus how they occurred in the 1960’s.

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Why is NHL facing unprecedented mumps outbreak?