Serological results, even if imperfect, should be a factor in the case definition. There is a continued need for a serological or biochemical test to detect infection early, analogous to the use of IgM for a single-serum early diagnosis of hepatitis A. Retrospective serological studies can be useful to determine if the disease is in- creasing in prevalence or spreading to new areas. Control What pragmatic measures can the state health departments take to control Lyme disease? It appears to be highly significant that this question remained unanswered. 709
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