ENVIRONMENTAL RISK-FACTORS FOR LYME-DISEASE IDENTIFIED WITH GEOGRAPHIC INFORMATION-SYSTEMS

Objective. A geographic information system was used to identify and lo cate residential environmental risk factors for lyme disease. Methods. Data were obtained for 53 environmental variables at the residences o f Lyme disease case patients in Baltimore County from 1989 through 199 0 and compared with data for randomly selected addresses. A risk model was generated combining the geographic information system with logist ic regression analysis. The model was validated by comparing the distr ibution of cases in 1991 with another group of randomly selected addre sses. Results. In crude analyses, 11 environmental variables were asso ciated 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. Residen ce 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. Conclusions. Combining a geo graphic information system with epidemiologic methods can be used to r apidly identify risk factors of zoonotic disease over large areas.