Spatial patterns of dengue cases and Wolbachia Occurrence in Aedes mosquitoes in a persistent endemic area of Samarinda, East Kalimantan, Indonesia

Abstract

Persistent dengue endemicity remains a major public health concern in tropical and subtropical regions. Spatial analysis offers critical insights into transmission dynamics and hotspot distribution, supporting more targeted interventions. This study examined persistent dengue transmission in a hyperendemic setting by evaluating vertical transmission, Wolbachia establishment, and spatial heterogeneity. The epidemiological analysis included all 1,081 laboratory-confirmed dengue cases reported between January and December 2024 across 59 villages in Samarinda, East Kalimantan, Indonesia. A nested entomological survey included all 150 eligible households of laboratory-confirmed dengue cases identified during field surveillance between June and September 2024 across 40 villages, using 300 indoor and outdoor ovitraps. Female Aedes aegypti reared from field-collected eggs and egg samples were tested for DENV, while female Aedes aegypti were screened for Wolbachia . Spatial patterns were evaluated using Global Moran’s I, Local Moran’s I, and Getis-Ord Gi statistics. Forty of 59 villages (67.8%) were classified as highly endemic. DENV was not detected in the adult mosquito and egg samples tested. Wolbachia was detected at 39.9% of trapping locations with valid molecular results. Dengue incidence showed significant spatial clustering, whereas Wolbachia occurrence was spatially heterogeneous and overlapped with some dengue hotspots. Failure to detect DENV in the tested samples does not exclude rare vertical transmission. Likewise, the spatial co-occurrence of Wolbachia and dengue hotspots cannot establish the origin or epidemiological effectiveness of Wolbachia . Nevertheless, the integrated surveillance approach provides a useful framework for targeted, context-specific dengue surveillance and vector-control planning.