BACKGROUND: The objective was to compare the clinical features of earlylocal Lyme Disease: Erythema Migrans (EM) between two highly endemic areas: New York State and NortheasternPoland. Study was based on self reporting questionnaires, physical examination, and laboratory results.MATERIAL/METHODS: Group I (n=27) consisted of citizens from New York State presenting with EM, referredto the study by their physicians. Group II (n=25) consisted of patients treated as outpatients in 1998-1999at the Department of Infectious Diseases and Neuroinfections, Medical University of Bialystok, Poland.The diagnosis of EM was based on patient history and clinical picture. RESULTS: Depending on the immunereaction of the host, the clinical picture is variable. The initial symptoms range from discrete to stronglyexpressed. The inflammatory reaction at the site of tick-bite seems to be milder in Europe than in NorthAmerica, which is reflected in the prevalence of the annular form of rash and milder expression of generalsymptoms. Mild or absent general symptoms and the prevalence of the annular over homogenous form areobserved in those areas of Europe where Ixodes ricinus is the main vector. In the endemic area of NewYork State, where Ixodes scapularis mainly occurs, uniform EM with flu-like symptoms is more common.CONCLUSIONS: There are distinct differences in the typical clinical pictures between the two separatedendemic areas of New York State and Northeastern Poland, due to different vectors (saliva components?),bacterial genospecies, likely intermediate hosts and climatic differences. Familiarity with the presentingform of the disease can be very important, especially for primary care physicians.

Keywords: Comparative Study, Erythema, Lyme Disease, New York, Poland, Time Factors