Human granulocytic ehrlichiosis in Northern California: two case descriptions with genetic analysis of the Ehrlichiae.

We report two cases of human granulocytic ehrlichiosis (HGE) that occurred in northern California in summer 1998. Patients had fever, malaise, and myalgia, reported tick bites, had moderate thrombocytopenia, and had normal or slightly elevated liver enzyme activities. Ehrlichial inclusions were observed in the blood of one patient, and HGE-agent DNA was amplified by PCR from both patients. Genetically, the strains resembled horse isolates from northern California. The close spatial and temporal proximity of the two new cases may be due to a nidus of infection in the area or heightened surveillance by local physicians.