Asymptomatic Borrelia burgdorferi infection.

Little is known about the natural history of asymptomatic Borrelia burgdorferi infection. Our analysis of the asymptomatic infections diagnosed serologically in a recent OspA vaccine trial conducted in the United States (N Engl J Med 1998;339: 209-215), suggests that the natural history of this event is more benign than that reported for untreated patients with erythema migrans (Ann Intern Med 1987;107: 725-731). We hypothesize that this is due either to incorrect diagnosis since the specificity of the serologic criteria used to diagnose asymptomatic infection in the vaccine study is unknown, or to infection with non-pathogenic strains of B. burgdorferi. Increasing evidence indicates that the invasive potential of strains of B. burgdorferi varies according to the specific subtype. Theoretically, a serologic testing method could be devised which would distinguish infection with invasive versus non-invasive strains of B. burgdorferi, and allow testing of the second hypothesis.