Case cluster shifting and contaminant source as determinants of melioidosis in Taiwan

Objectives To assess the geographical distribution of melioidosis contamination sources and the association between the location of melioidosis cases and positive sampling sites for Burkholderia pseudomallei in Taiwan. Methods Data on the location of melioidosis cases from 2002 to 2011 were combined with the geographical distribution of B.similar to pseudomallei as indicated by the detection of specific flagella gene products measured from 2005 to 2011. Temporal and spatial analyses were used to determine the incidence, cluster shifts and associations between the two datasets. Results Melioidosis cases clustered in two hot-spot areas with incidence rates that were significantly higher than in neighbouring towns. The incidence rates in the northern area gradually decreased, while the rates in the southern area increased and were temporally associated with the appearance of B.similar to pseudomallei-specific flagella genes in water samples. Conclusions Melioidosis hot-spot areas were present in Taiwan. Water contaminated with B.similar to pseudomallei serves as a potential transmission vehicle and is correlated with an increase in melioidosis cases; this correlation was stronger than that for B.similar to pseudomallei-contaminated soil.