Mumps Outbreaks at Four Universities — Indiana, 2016

Mugdha Golwalkar, MPH; Brian Pope; Jill Stauffer, MS; Ali Snively; Nakia Clemmons, MPH

Disclosures

Morbidity and Mortality Weekly Report. 2018;67(29):793-797. 

In This Article

Investigation and Results

On January 20, 2016, a student with unknown mumps vaccination history was evaluated at university A's student health center for parotid swelling. The student reported a possible mumps exposure at a university outside Indiana, where a large mumps outbreak was occurring. Mumps immunoglobulin M (IgM) testing was negative, but continuing parotitis motivated the university to request reverse transcription–polymerase chain reaction (RT-PCR) testing at ISDHL 2 days later, and results were positive for mumps. By February 17, 2016, two additional cases at university A were confirmed by RT-PCR. On January 25, a fully vaccinated student was evaluated at university B's student health center with parotid swelling, headache, and fever. Mumps was suspected and reported to ISDH; however, laboratory testing was not conducted. On February 12, three additional mumps cases with epidemiologic links to the index case were confirmed by RT-PCR at university B. On March 11, three cases were confirmed by RT-PCR at university C, with no epidemiologic links among the patients or to any outside case. On April 2, three cases (one confirmed by RT-PCR and two epidemiologically linked) were identified at university D; all patients reported possible exposures to mumps during a spring break trip to Florida 2 weeks before symptom onset. Additional mumps cases occurred in all four universities and in the surrounding community, with the last onset date among university-affiliated cases on July 18, 2016.

Mumps RT-PCR testing was made available through the ISDHL. IgM testing was only offered through commercial laboratories. A protocol was developed to assist providers in ordering the right testing according to the time elapsed from symptom onset, collecting the correct specimens, and obtaining preauthorization for testing at ISHDL. Preauthorization required consultation with an ISDH epidemiologist to ensure patients with suspected mumps met clinical and epidemiologic criteria for testing and to ascertain exposure information to prioritize testing of specimens from patients without epidemiologic links to other cases or suspected cases in new settings. Odds ratios and comparison of proportions chi-squared tests were calculated to evaluate the impact of specimen collection timing and dissemination of testing guidance on specimen positivity. A subset of RT-PCR–positive specimens was sent to CDC's Viral Vaccine Preventable Diseases Branch for genotyping.

A total of 281 mumps cases (237 laboratory confirmed and 44 probable) were identified in all four outbreaks from January to September 2016. Among these cases, 179 (63.7%) occurred in university students or staff members (university-affiliated cases) and 102 (36.3%) in community members not affiliated with any of the universities (community cases) (Figure 1). Epidemiologic links to university cases were only identified in 25.5% of community cases. Signs and symptoms experienced by patients included parotitis (276, 98.2%), fever (109, 38.8%), headache (74, 26.3%), earache (60, 21.4%), jaw pain (16, 5.7%), malaise/body aches (11, 3.9%), and sore throat (10, 3.6%). Complications from mumps were infrequent, with one report of meningitis and five reports of orchitis.

Figure 1.

Number of confirmed (N = 237) and probable (N = 44) mumps cases associated with outbreaks at four universities, by week of onset and dates of MMR vaccination clinics — Indiana, January–September 2016
Abbreviation: MMR = measles, mumps, and rubella vaccine.

Receipt of 2 doses of MMR was documented for 152 (84.9%) of 179 university-affiliated cases and 53 (52.0%) of 102 community cases; 11 (3.9%) of the 281 cases had documentation of a positive immunoglobulin G titer. Twelve cases (4.3%) had documentation of ≥3 doses of MMR administered >4 weeks before parotid swelling onset. In six cases in which complications occurred, the persons had each received 2 doses of MMR. Seven vaccination clinics were held across three schools, and 5,273 doses of MMR were administered, most (3,106; 59%) at highly attended clinics at university B. Based on high 2-dose MMR coverage at each university, many of these doses likely were third doses.

ISDHL tested specimens from 490 suspected cases for confirmation by RT-PCR, 209 (42.6%) of which were positive. Among 407 cases of suspected mumps for which RT-PCR results and onset dates were available, 53.1% (146/275) of specimens collected within 2 days of parotitis onset were positive; this decreased slightly to 47.7% (63/132) for specimens collected ≥3 days after parotitis onset, and the change was not statistically significant (Table). Among 63 cases for which IgM results and onset dates were available, 34.3% (11/32) of specimens collected within 2 days of parotitis onset were positive; the rate of positivity increased to 61.3% (19/31) for specimens collected ≥3 days after parotitis onset (p<0.05). Among 18 cases for which specimens were collected within 5 days of parotitis onset and a RT-PCR test was positive, six had results that were IgM positive. Persons in 16 of these cases had received 2 MMR doses, and those in two cases had received a single dose. Weekly percent positivity of specimens submitted to ISDHL increased significantly from an average of 25.8% in the weeks before dissemination of the laboratory testing protocol to an average of 37.8% (p = 0.005) in the weeks after dissemination (Figure 2). CDC provided genotyping for 142 specimens; 140 (98.6%) were type G (the most common genotype circulating in the United States), and two were unable to be genotyped.

Figure 2.

Number and percentage of specimens testing positive for mumps by reverse transcription–polymerase chain reaction, by week — Indiana State Department of Health Laboratories, 2016

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