title: Extreme weather events and environmental contamination are associated with case-clusters of melioidosis in the Northern Territory of Australia.
abstract: BACKGROUND
  Melioidosis, the infection due to the environmental organism Burkholderia pseudomallei, is endemic to northern Australia and South East Asia. It is associated with exposure to mud and pooled surface water, but environmental determinants of this disease are poorly understood. We defined case-clusters in northern Australia, determined their contribution to the observed rate of melioidosis, and explored clinical features and associated environmental factors.
  
  
  METHODS
  Using geographical information systems data, we examined clustering of melioidosis cases in time and geographical space in the Top End of the Northern Territory of Australia between 1990 and 2002 using a scan statistic. DNA macrorestriction analysis, resolved by pulsed field gel electrophoresis, was performed on isolates from patients.
  
  
  RESULTS
  We defined five case-clusters involving 27 patients that occurred within 7-28 days and/or a radius of 100-300 km. Clustered cases were associated with extreme weather events or environmental contamination; no difference in the clinical pattern of disease was noted from other patients not involved in clusters. Isolates from patients linked to environmental contamination were caused by isolates with similar DNA macrorestriction patterns, but isolates from patients linked to severe weather events had more diverse DNA macrorestriction patterns.
  
  
  CONCLUSIONS
  Case-clusters of melioidosis where isolates exhibit diverse DNA macrorestriction patterns in our region are linked to extreme weather events and outbreaks where isolates are predominantly of the same DNA macrorestriction pattern are linked with contamination of an environmental source.
authors.affiliation: Tropical and Emerging Infectious Diseases Division, Menzies School of Health Research, Charles Darwin University, Australia. allenc@menzies.edu.au
authors.forename: Allen C
authors.initials: AC
authors.lastname: Cheng
authors.forename: Susan P
authors.initials: SP
authors.lastname: Jacups
authors.forename: Daniel
authors.initials: D
authors.lastname: Gal
authors.forename: Mark
authors.initials: M
authors.lastname: Mayo
authors.forename: Bart J
authors.initials: BJ
authors.lastname: Currie
mesh_terms: D016957:Burkholderia pseudomallei / Q000145:classification / Q000235:genetics; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000235:genetics; D004190:Disasters; D004196:Disease Outbreaks; D016521:Electrophoresis, Gel, Pulsed-Field / Q000379:methods; D004783:Environmental Microbiology; D006801:Humans; D008554:Melioidosis / Q000453:epidemiology* / Q000382:microbiology / Q000635:transmission; D015876:Northern Territory / Q000453:epidemiology; D014887:Weather; D014919:Wind
chemical_list: D004269:DNA, Bacterial