Ehrlichia chaffeensis multiplies in the phagosome of leukocytes, particularly monocytes. Infection may be asymptomatic or present with headache, high fever, myalgia, and malaise. Children are more likely to present with a rash (66%) than adults (33%). Gastrointestinal symptoms are also more likely in children. The maculopapular rash is seen less commonly on the palms and soles than with Rocky Mountain spotted fever (RMSF), but symptoms may be very similar between RMSF, ehrlichiosis, and anaplasmosis. Ehrlichiosis can cause serious or fatal disease, but not as frequently as RMSF. Only about 50% of patients are hospitalized and the fatality rate is low (3%) and primarily seen in immunosuppressed and asplenic patients.