Abstract
BACKGROUND: On the 2nd and 3rd December 2023, a cluster of nine acute febrile illnesses with parotidomegaly was reported among students of a kindergarten in a South-West coastal district of India. We investigated the outbreak to identify the illness, to describe the outbreak in terms of time, place and person, to identify the factors responsible for the spread, and to control the disease. METHODS: The investigation was conducted in a military setting at a South-West coastal district of India from December 2023 to January 2024. Clinical and epidemiological data of the initial cases were captured using a data abstraction sheet from healthcare establishments, kindergartens and schools to make operational case definitions. We did an active house to house surveillance to detect additional cases till 26 January 2024, i.e. for six weeks after the last case was detected. The descriptive analysis was done by calculating the incidence as per age, gender and vaccination status, plotting of an epidemic curve and preparation of spot maps to understand the spread of cases. We also conducted a matched case-control study to test the hypothesis that clustering of unvaccinated kindergarten students was the cause of this Mumps outbreak. RESULTS: The index case was identified as Mumps on 02 December 2023 in the Paediatric department of the hospital. A total of 52 cases of Mumps occurred with an attack rate of 1.8%. Forty-five out of the 52 affected children were from Kindergarten and the rest from primary and middle school. The outbreak started on 02 November 2023, peaked on 04 December 2023 and ended on 15 December 2023 after rapid institution of control measures. The incidence was highest (5.5%) in children aged four and five years. There was clustering of cases in kindergarten. Nearly 60% of the cases were unvaccinated against Mumps. Vaccination against Mumps was found to be protective against Mumps. CONCLUSION: This outbreak of Mumps was probably due to close interaction of unvaccinated children in the kindergarten. Students contracting Mumps lose classes and the disease is known to cause complications when occurring later in life. Hence, we recommend Mumps vaccination during childhood to prevent such outbreaks.