Residential setting as a risk factor for Lyme disease in a hyperendemic region.

The hypothesis that residence in a uniform medium-density residential development is associated with lower incidence of Lyme disease is tested with data from a rural, 12-town region of south-central Connecticut where the disease is hyperendemic. The residential setting for 424 cases identified by active surveillance from 1993 through 1995 was determined. Cases located within the Eastern Coastal ecologic region, where tick densities are known to be higher than inland and where most of the population in the region resides, were selected for further analysis. Within this region, residence in a homogeneous area of medium-density development at least 30 acres (12 ha) in size was associated with a two- to 10-fold lower level of risk than residence in surrounding less developed areas, depending on the estimate of residential population. Type of residential development may be an important factor to consider, in addition to other environmental variables, in studies of peridomestic vector-borne disease in human populations.