Local wastewater monitoring as a complementary tool in a mumps outbreak investigation in the Netherlands: A proof-of-concept study

BACKGROUND: A recent outbreak of mumps showed a concerningly low number of classical disease notifications, prompting evaluation of the efficacy of local wastewater monitoring. METHODS: Suspected mumps cases were recorded by local General Practitioner practices (n = 13) for 20 weeks, and laboratory-reported notifications were collected. Local wastewater monitoring using passive samplers was deployed downstream of a confirmed case and their school, and in wastewater pumping stations serving the involved and neighbouring towns. Wastewater samples were analysed using reverse transcription polymerase chain reaction. RESULTS: General Practitioners reported 50 suspected patients, of which 24 were confirmed. The passive sampler near the confirmed case detected virus RNA directly postdiagnosis, followed by a negative signal afterwards, while samplers at the school and the local pumping station detected rising concentrations as more cases were reported. Samplers in neighbouring towns showed further spread, including a town with no reported cases. CONCLUSION: This study demonstrates the first successful proof-of-concept for local wastewater monitoring of mumps and indicates a possible correlation between wastewater and clinical monitoring. These results suggest a role for local wastewater monitoring using passive samplers in creating situational awareness during an outbreak, even when cases are not reported.