An investigation of mumps outbreak in a school, Wang Chin District, Phrae Province, May–October 2019

Abstract

Backgrounds: On 30 July 2019, Situation Awareness Team of Department of Disease Control received a notification that there was a cluster of mumps cases in a school, Wang Chin District, Phrae Province. Joint Investigation Team performed an investigation during 6–8 August 2019 to confirm the diagnosis and the existence of the outbreak, to describe epidemiological characteristics, to determine the risk factors of mumps transmission and to provide appropriate control measures.
Methods: Active case finding was performed by screening of students, teachers and school officers. A suspected case was defined as any person in a school who had at least one of the following symptoms and signs of: pain/swelling/tenderness at one or more saliva glands or testis which cannot been explained by other more likely cause during 16 May to 1 October 2019. Confirmed case was suspected case who has positive reverse transcription polymerase chain reaction for mumps virus or positive for serum mumps IgM. Environmental survey of school was carried out. The coverage of mumps–containing vaccine (MuCV) and vaccine effectiveness were determined. A retrospective cohort was done in 371 persons in school to identify potential risk factors of transmission.
Results: There were 60 mumps cases among students and teachers in the school, of which 16 were confirmed. Overall attack rate was 15.6%. The highest attack rate was found in primary school grade 5 (42.4%). The median age of cases was 10.6 years (IQR=1.2). Common symptoms included saliva gland pain, saliva gland swelling and fever (93.3%, 91.7%, and 60.0% respectively). The MuCV coverage of at least one dose was 48.3% and two doses were 6.0%. The vaccine effectiveness of receiving two doses of MuCV was 71.6%. Shared water glasses (adjusted OR=2.30, 95% CI=1.21–4.38) was identified as the risk factor of disease transmission. Conclusion: There was a confirmed mumps outbreak in the school. Most of cases are the students in primary school grade 5. Shared water glasses are the risk factor for disease transmission. Screening sick students, isolation, and avoid sharing objects might curtail the outbreak.