Notes from the Field : Absence of Asymptomatic Mumps Virus Shedding Among Vaccinated College Students During a Mumps Outbreak — Washington, February–June 2017

Abstract

A suspected case of mumps in a member of a fraternity or sorority at the University of Washington (UW), Seattle, Washington, USA, was reported on 8 February 2017, and by 19 July 2017, a total of 42 (16 confirmed and 26 probable) mumps cases were reported among UW students and associated community members, with symptom onset during 6 February-4 June 2017. Among the 42 cases, 32 (76%) occurred in fraternity and sorority members. Of these, 12 (37.5%) were confirmed and 20 (62.5%) were probable cases. Cases occurred in residents in 20 (38.5%) of 52 fraternity and sorority houses that lodged 2259 (48.6%) of 4646 total fraternity and sorority members on the campus. All mumps patients had received >=2 documented doses of measles-mumps-rubella (MMR) vaccine; the 2-dose MMR coverage among all UW students exceeded 99%. Genotyping of viral isolates from 4 confirmed mumps cases identified genotype G in all 4. During 6-9 March, 235 doses of MMR vaccine were administered to members of the 8 fraternity and sorority houses reporting the highest number of cases. Asymptomatic mumps virus shedding was assessed in 160 vaccinated students. They reported the following symptoms during the preceding month, none of which required hospitalization: fever (n=10, 6%), cough (n=55, 34%), sore throat (n=37, 23%), and swelling or pain of the parotid gland or jaw not attributable to dental problems (n=8, 5%). Buccal swabs from all 160 students were mumps-virus negative by real-time reverse transcription-polymerase chain reaction. This evaluation found no laboratory evidence of asymptomatic mumps virus shedding.