Coexposure to Borrelia burgdorferi and Babesia microti does not worsen thelong-term outcome of Lyme disease

Previous studies suggest that concurrent Lyme disease and babesiosis produc e a more sever illness than either disease alone. The majority of babesiosi s infections, however, are subclinical, Our objective was to characterize o n the basis of a total-population survey of Nantucket Island, Massachusetts , whether coexposure to Lyme disease and babesiosis causes more severe illn ess or poorer long-term outcomes than Lyme disease alone. In this retrospec tive cohort study, residents indicating a history of Lyme disease were comp ared with randomly selected population controls on a standardized medical h istory, blinded physical examination, and serological studies for Borrelia burgdorferi and Babesia microti. Serological evidence of exposure to babesi osis was not associated with increased severity of acute Lyme disease. The groups did not differ with regard to the prevalence of constitutional, musc uloskeletal, or neurological symptoms a mean of 6 years after acute Lyme di sease. Prior Lyme disease and serological exposure to B. microti are not as sociated with poorer long-term outcomes or more persistent symptoms Lyme di sease alone.