Spatial and Temporal Analyses of Melioidosis in Kaohsiung, Taiwan

Melioidosis, a fatal infectious disease caused by the saprophytic bacterium Burkholderia pseudomallei, is endemic to Kaohsiung, Taiwan. To assess potential exposure to the pathogen among residents, seropositivity to the B. pseudomallei flagella protein was measured, revealing an overall positivity rate of 14.6%, with peak rates observed in individuals ages 10-19 and 80-99 years old. Geographical analysis identified seropositivity clusters (>16%) spanning northern, central, and southern Kaohsiung, whereas clinical cases were concentrated in the northern (Qieding district) and central regions (Zuoying and Nanzi districts). Spatial autoregression using the Moran I revealed a prominent central cluster, with SaTScan and Ripley K function analyses confirming cluster radii of 6.2-8.8 and 6.4-6.7 km, respectively. These clusters encompassed Zihguag, Nanzi, and Zuoying districts, where 454,000-513,000 residents were potentially exposed to B. pseudomallei over a 20-year period (2003-2024). Melioidosis incidence peaked in 2005 (8.5 cases per 100,000 people), 2009-2011 (15.6-23.4 cases per 100,000 people), and 2024 (28.2 cases per 100,000 people), coinciding with catastrophic typhoons. Annual melioidosis incidence within the hot spot correlated with rainfall intensity during typhoon events. Flooded areas caused by typhoons overlapped with the hot spot, inundating 38-43% of the region. Higher B. pseudomallei polymerase chain reaction positivity rates (11-22%) were detected in northern rivers flowing through the hot spot compared with lower rates (0-7%) in southern or eastern nonhot-spot areas. These findings suggest that typhoon-related flooding may contribute to the formation of melioidosis hot spots in Kaohsiung.