Spatial epidemiology of an adenovirus outbreak at the Vietnam National Children's Hospital in Hanoi, Vietnam.

OBJECTIVES: Adenovirus disproportionately affects children, with limited surveillance in low- and middle-income countries such as Vietnam. METHODS: We mapped the spatial distribution of laboratory-confirmed cases during a 2022 outbreak at Vietnam National Children's Hospital (VNCH) to identify areas with elevated case reporting. We analysed laboratory-confirmed adenovirus cases admitted to VNCH (January-October 2022), examining demographics and location. ArcGIS Pro was used to map case location and assess spatial clustering using Global Moran's I, Optimized Hot Spot Analysis, and Local Moran's I (LISA), followed by sensitivity analyses and evaluation of spatial efficiency using the predictive accuracy index (PAI). RESULTS: Of 2687 cases, 89% occurred in children aged <5 years, predominantly boys (61%). Most cases were reported from Hanoi (74%). Spatial analysis revealed significant clustering, with hotspot communes concentrated in 12 core urban districts that were consistently detected across three sensitivity analysis specifications. LISA identified 83 High-High cluster communes, accounting for 44.3% of all Hanoi cases, and demonstrated the highest spatial efficiency (PAI = 9.37). Coldspots were primarily located in the outer districts. CONCLUSION: The observed spatial pattern is likely to reflect an indirect distance effect on case reporting to VNCH rather than true community-level disease intensity. These findings may support hospital-level surveillance and outbreak preparedness in resource-limited settings.