The Role of Climate in the Epidemiology of Melioidosis

PURPOSE OF REVIEW: Melioidosis epidemiology is susceptible to climate change through direct and indirect effects on human encounter with the causative agent, Burkholderia pseudomallei. This review describes the current depth of knowledge and recent advances in the understanding of this relationship and applies it to observations of melioidosis in Western Australia. RECENT FINDINGS: High maximum rainfall and dense cloud cover have been shown to predict environmental presence of B. pseudomallei and cases of melioidosis, probably through correspondingly high moisture levels in B. pseudomallei-receptive soils. Increased melioidosis cases have been observed following storms in Taiwan and cyclones in the Australian Northern Territory and strengthen the association between melioidosis and extreme weather events. Indirect weather effects contribute to bacterial exposure through mechanisms such as increasing B. pseudomallei output from water seeps after heavy rain or localised flooding. Climate and weather have been directly implicated in dissemination of B. pseudomallei and cases of melioidosis in several notable events in Western Australia. Over a 10-year surveillance period, the cases that lay in the path of a tropical cyclone co-located with cyclone systems that repeatedly crossed the Western Australian coast. Cyclone-associated cases were caused by different B. pseudomallei MLST genotypes, arguing against airborne dissemination from a common source. SUMMARY: Predicted increases in temperature, changes in global precipitation patterns and an increased incidence of extreme weather events are expected to change melioidosis epidemiology. Further studies of the physical geographic drivers of melioidosis will deepen understanding of the impact of climate on melioidosis.