Human ehrlichiosis: prospective active surveillance in febrile hospitalized patients.

Between 1 April 1987 and 30 September 1988 prospective active surveillance of human ehrlichiosis was conducted among febrile patients hospitalized in southeast Georgia. If disease of the immune system, bacterial infection, pneumonia, or surgical illness was documented by the end of the first full day of hospitalization, the patient was excluded. Of 75 patients enrolled in the study, 8 (10.7%) had a fourfold rise or fall in titer to Ehrlichia canis (case-patients). The rate was 5.3 cases/100,000 population. Case-patients were more likely than noncase patients to have become ill in May or June (P = .008) and to report a recent tick bite (P less than .001). At hospital admission, case-patients had lower white blood cell counts (median, 4,450/mm3; P = .001), platelet counts (median, 133,000/mm3 P less than .001), and higher aspartate aminotransferase (median, 68 IU/ml; P = .004) and alanine aminotransferase levels (median, 62 IU/ml; P = .038).