A geographic information system was used to identify and locate residential environmental risk factors for
Data were obtained for 53 environmental variables at the residences of
Lyme disease case patients in Baltimore County from 1989 through 1990 and compared with data for randomly selected addresses. A risk model was generated combining the geographic information system with logistic regression analysis. The model was validated by comparing the distribution of cases in 1991 with another group of randomly selected addresses.
In crude analyses, 11 environmental variables were associated with
Lyme disease. In adjusted analyses, residence in forested areas (odds ratio [OR] = 3.7, 95% confidence interval [CI] = 1.2, 11.8), on specific soils (OR = 2.1, 95% CI = 1.0, 4.4), and in two regions of the county (OR = 3.5, 95% CI = 1.6, 7.4) (OR = 2.8, 95% CI = 1.0, 7.7) was associated with elevated risk of getting
Lyme disease. Residence in highly developed regions was protective (OR = 0.3, 95% CI = 0.1, 1.0). The risk of
Lyme disease in 1991 increased with risk categories defined from the 1989 through 1990 data.
Combining a geographic information system with epidemiologic methods can be used to rapidly identify risk factors of zoonotic
disease over large areas.