Actually, the times have already changed, but not everyone realizes it. This article is a nice, concise report of a 2014 mumps outbreak at a college that confirms prior observations on diagnosis of mumps in the current era, as well as providing very important lessons for primary care providers.
Source: Patel LN, Arciuolo RJ, Fu J, et al. Mumps outbreak among a highly vaccinated university community-New York City, January-April 2014. Clin Infect Dis. 2017;64(4):408-412; doi:10.1093/cid/ciw762. See AAP Grand Rounds commentary by Dr. Rebecca Brady (subscription required).
The school, in New York City, isn't named in the publication, but this doesn't really matter. College outbreaks of mumps are relatively common in the US, and all healthcare providers need to be capable of evaluating and managing patients with possible parotitis. The report encompasses 56 cases of mumps, and it is clear that practitioners missed the first 2 cases in the outbreak; if they had been recognized, it likely would have prevented most of the subsequent cases. But, we can learn much from these early missteps.
We have 2 problems in mumps management. Today in the US, recent primary care residency graduates may have never seen a case of parotitis. That's a good thing, universal immunization has been very effective; the downside is we have less experienced practitioners evaluating such patients. Second, even for the old codgers like me who have seen a lot of mumps cases, the tried and true diagnostic test, mumps IgM antibody determination, doesn't work as well as in the bad old days. This study illustrates these 2 problems well.
Practitioners evaluating the first case presenting to the school's health center actually had mumps IgM antibody sent, because the providers were concerned about the diagnosis. However, when that test returned as negative, they dismissed a diagnosis of mumps. Ultimately, mumps IgM antibody detected only 2 of 44 cases in which that test was sent, similar to other reports. The better test, mumps PCR testing on a buccal swab, was positive in 27 of 40, still not great, but timing is everything in mumps testing. For example, PCR was positive in 83% of cases tested with less than 48 hours' clinical symptoms, versus 44% if symptoms were present for 2 days or more. The phenomenon of poor mumps IgM sensitivity is mainly a phenomenon of highly vaccinated patients, where IgM response can be delayed and/or blunted. Clearly, negative mumps IgM antibody doesn't exclude the diagnosis.
Also, it's important to recognize that mumps vaccine efficacy is good but not great. The CDC summarized (see Table 1 on page 9) median protection rate after 1 vaccine dose at 78% (range 49 - 92%) and after 2 doses of 88% (66 - 95%). Also, waning vaccine immunity and new circulating mumps genotypes might adversely affect protection rates in a college population.
I see 4 take-home points for all of us evaluating individuals for parotitis:
1. Take time now to refresh your mumps knowledge.
2. For patients suspected of parotitis (jaw swelling, erythema of the parotid duct, pain with citrus ingestion are good clues), send both mumps IgM serum antibody and mumps PCR on buccal swab for testing; keep the individual quarantined until results are available.
3. Even if both tests are negative, if there is a history of exposure to another individual with parotitis, the odds that this is still mumps go way up; many viruses can cause parotitis, but only mumps is known to cause epidemic disease.
4. Ensure your patients are adequately immunized. Even an 88% protection rate is likely good enough to prevent epidemic spread, and this current rate is what resulted in those young US providers never having seen a case of mumps!
Oh, and of course ".... keep your eyes wide, the chance won't come again"
