Uncovering the scale and link of two SARS-CoV-2 outbreaks in nursing homes by combining integrated genomic surveillance, contact tracing, and point-of-care testing

Abstract

Abstract Aim The local public health authority (LPHA) in Duesseldorf received notification of two SARS-CoV-2 outbreaks in nursing home A and nursing home B in October 2021 and embarked on an outbreak investitation to identify the source of the outbreak and epidemiological links between cases. Subject and methods The LPHA conducted a retrospective outbreak investigation involving residents and staff and combined results of active case finding, weekly point-of-care testing (POCT), and integrated genomic surveillance (IGS) with structured case interviews, whole-genome sequencing, and cluster analysis. Results The LPHA identified two linked outbreaks of SARS-CoV-2 infections in nursing homes A and B, with a total of 32 cases occurring from 12 to 29 October 2021. First case notification and routine contact tracing revealed a cluster of six SARS-CoV-2 cases in nursing home A and two cases in nursing home B. Weekly POCT independent of symptoms and IGS data revealed that the true extent of the outbreak involved 27 cases associated with nursing home A and five additional, genetically identical cases that were linked to nursing home B. Routine contact tracing identified 20.0%, POCT 33.3%, symptom-driven testing 36.7%, and IGS 10.0% of all subsequent cases in this outbreak. Using IGS data, the link between both outbreaks was verified. Conclusion As routine contact tracing may be of limited feasibility and accuracy in nursing homes, the use of frequent POCT of staff and residents irrespective of symptoms in combination with the use of IGS data proves to be a valuable approach for effective identification of transmission networks and facilitates prompt outbreak interventions.