260
Whatisinterestingisthatmoreofthe44outbreakswerecausedbyhotand
coldwatersystems(25%)thanbyanyothertypeofsystem.Thischallengesthe
oftenheld assumption that cooling towers causemost outbreaks. However,
while cooling towers caused fewer outbreaks in this study, they did cause
most of the individual cases of disease. Spa pool also were implicated in
causing14%of theoutbreaks, althoughmost of thecases linked to spapools
areclassedasPontiacFever andnot classicLegionnaires’Disease.
OutbreaksbyFailing (n=24 from17outbreaks)
This chartprovides informationas to thecausesof individual outbreaks.
Byaconsiderablemargin, problemswith the“SchemeofControl”havebeen
regardedas the failing that led to theoutbreak.This strongly emphasizes the
need forclear,distinctactions,whichwould include taskssuchasmonitoring
of temperatures, flushing of little used outlets, inspection of water storage
0 10 20 30 40 50 60 70
RiskAssessment
Schemeof Control
Cleans andDisinfections
TrainingandCompetence
