Figure 1. Study population and number of patients with clinician-diagnosed Lyme disease in the MarketScan database, United States, 2005–2010. *Persons not enrolled for the full 12 months of any year and who did not have prescription data were removed from both the numerator and denominator for rate calculations. Therefore, removal of these persons did not substantially affect rate calculations and the final estimated number of cases. †One repeat inpatient was excluded (admitted in a subsequent year but <365 days after initial admission). No repeat admissions occurred >365 days after initial admission. ‡A total of 2,945 repeat outpatients (seen in a subsequent year but <365 days after previous year’s visit) were excluded (Technical Appendix). ICD–9, International Classification of Diseases, Ninth Revision.