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Mumps Outbreak At Keystone Ski Resort Infects 19 And Counting

Allison M. Maiuri
A particle of the mumps virus.

Health officials are investigating an outbreak of mumps that started among employees of Keystone Resort in Colorado. Of the 19 cases identified so far, 18 of them are resort employees. 

“It’s not going to be surprising to see that number change as our investigation continues,” said Sara Lopez, nursing manager with Summit County Public Health, which identified the first three cases about a month ago. She said at this point it’s unclear how the one non-employee came down with the illness. 

The viral infection causes painful swelling in the cheeks and jaw, in addition to fever, fatigue and headaches. The MMR vaccine, which most people now receive as children, protects against measles, mumps and rubella. But while it’s typically thought to offer a lifetime of protection against two of those diseases, protection against mumps can sometimes wear off over time.

Lopez said it’s “a bit of a mixed bag” among those who fell ill so far; some weren’t vaccinated, some were fully vaccinated and others have an unknown immunization history.

Mumps cases can fluctuate from year to year. For example, Colorado saw four cases in 2014 and 83 cases in 2017. Last year, a 15-person outbreak among detainees at an ICE detention center in Aurora brought the state’s total cases to 67. 

About nine out of 10 people who receive both doses of MMR gain protection against mumps, but the combination of prolonged contact and waning immunity means outbreaks can happen in groups that are well-vaccinated. For example, in the last couple years a large outbreak happened at a university where 98% of students were vaccinated, and another happened in military recruits living in the same compound even though 91% of them were fully vaccinated. 

“Those can occur often in situations like college dormitories or sports teams or in close knit communities where there’s this continued exposure to the virus that can overcome the protection offered by the vaccine,” said Meghan Barnes, a vaccine-preventable disease epidemiologist with Colorado’s public health department. 

Barnes added that the risk to the general population, including skiers at the resort, is likely low.

“We think that the vaccination coverage overall in Summit County is pretty good,” she said. “So for people outside enjoying the outdoors who have passing contact with an employee and they're protected by the vaccine, we think they should probably have enough protection to not get sick from that minimal exposure.”

According to research published in the New England Journal of Medicine, giving people an MMR booster during an outbreak can help control its spread, and lower an already-vaccinated person’s chance of getting the illness by 78%. 

Earlier this month, the local health department held a clinic at Keystone, where they gave 35 shots of MMR to employees who live or work in close contact with those who got sick. Sara Lopez said another 30 received the vaccine this week.

“We are continuing to work closely with our local public health agencies,” said Loryn Roberson, communications manager with Keystone Resort. “We are also providing educational information and materials to our employees and offering vaccination clinics. As always, we encourage our employees and guests to take the appropriate precautions to mitigate the spread of colds, flu viruses and other contagious illnesses.”

People can spread mumps in coughs, sneezes and spit, starting a few days before symptoms appear and ending a few days after. It usually takes more than two weeks after exposure before symptoms show up. According to the Centers for Disease Control and Prevention, in some cases mumps infection can cause complications including brain infections, swollen ovaries and shrunken testicles.

This story was produced by the Mountain West News Bureau, a collaboration between Wyoming Public Media, Boise State Public Radio in Idaho, KUER in Salt Lake City, KUNR in Nevada, the O’Connor Center for the Rocky Mountain West in Montana, and KRCC and KUNC in Colorado.

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