Racial differences in reported Lyme disease incidence.

In the United States, the incidence of Lyme disease is considered to be disproportionately high among Whites because of risk of exposure. For assessment of racial differences in Lyme disease incidence and the role of risk exposure, incidence rate ratios (IRRs) for Lyme disease and its manifestations between Whites and African Americans in Maryland and in its focus of endemicity, the Upper Eastern Shore, were calculated. Calculations were based on reported cases of Lyme disease in Maryland during the years 1992-1996. The IRR for Lyme disease between Whites and African Americans was 6.3 (95% confidence interval (CI): 5.0, 8.0), decreasing to 1.8 (95% CI: 1.2, 2.7) for the Upper Eastern Shore. Statewide, there was a significant difference between the White to African American IRR for erythema migrans and for Lyme disease-associated arthritis, at 17.7 (95% CI: 11.2, 27.8) and 2.3 (95% CI: 1.7, 3.2), respectively. On the Upper Eastern Shore, the IRR for arthritis reversed, indicating higher incidence among African Americans than among Whites: IRR = 5.7 (95% CI: 2.4, 13.9) for erythema migrans and IRR = 0.7 (95% CI: 0.4, 1.1) for arthritis. White patients were more likely to have erythema migrans (risk ratio = 2.8, 95% CI: 1.9, 4.1) and less likely to have arthritis than were African Americans (risk ratio = 0.4, 95% CI: 0.3, 0.5). Among all patients, there was a significant negative association between arthritis and erythema migrans. Although much of the racial disparity in incidence rates diminishes in a rural, endemic area, consistent with exposure risk being responsible for much of the variation, a difference remains. This may be due to failure to recognize early disease (erythema migrans) among African Americans, resulting in increased rates of late manifestations. Geographic spread of the disease warrants efforts to increase awareness of Lyme disease and its manifestations among people of color and the health care providers who serve them.