Purpose:
To investigate the spatial and temporal distribution of patientresidence for Acanthamoeba keratitis cases diagnosed at UICbetween June 1, 2003 and September 1, 2007.
Methods:
A retrospective cohort of all Acanthamoeba keratitis patientsdiagnosed at University of Illinois Eye and Ear Infirmary (IEEI)between June 1, 2003 and June 1, 2007 was used with geographicinformation system (GIS) modeling and mapping software in adescriptive analysis to compare case residence at diagnosisover time. Cumulative annual incidence (CIR) rates per zip codewere calculated from 2003 Census data adjusting for total years,and overlie 2003 Census Chicago population density plotted byquartile. CIR categories were chosen to reflect EPA exposureclasses used in risk analysis.
Results:
The 6/03 - 6/05 Acanthamoeba keratitis CIR map demonstratesthat observed cases are distributed to the west, south and southwestand further from Lake Michigan compared to expected 2003 populationdistribution (Fig. 1), while the 6/03 - 6/07 Acanthamoeba keratitisCIR map shows cases continue presenting from the far west, southand southwest, but also present closer to Lake Michigan andthe city center (Fig. 2).
Conclusions:
This exploratory analysis indicates a changing AK case distributionwith time that is inconsistent with previously identified riskfactors, especially given lens solution base disinfectants areunchanged over the past dozen years without AK outbreaks, andsupports the potential potable water contribution to AK.
Keywords: Acanthamoeba • clinical (human) or epidemiologic studies: prevalence/incidence • amoeba