There are limitations to these data. ED visit rates are the number of emergency department (ED) visits where the primary diagnosis was the stated condition, per 100,000 population. Only visits made by Maryland residents to Maryland hospitals were used for the analysis; ED visits made by Maryland residents to out-of-state hospitals were not included. Data were obtained from the Maryland Health Services Cost Review Commission and are coded by county of residence. Cases are defined as ED visits that resulted in a hospital admission added to visits that did not result in a hospital admission where the primary diagnosis was the stated condition. These rates have not been age-adjusted.