NOTE: A surveillance case definition is a set of uniform criteria used to define a disease for public health surveillance. Surveillance case definitions enable public health officials to classify and count cases consistently across reporting jurisdictions. Surveillance case definitions are not intended to be used by healthcare providers for making a clinical diagnosis or determining how to meet an individual patient’s health needs.
A tick-borne febrile illness most commonly characterized by acute onset, accompanied by headache, myalgia, rigors and/or malaise; clinical laboratory findings may include: intracytoplasmic microcolonies (morulae) in leukocytes of peripheral smear, cerebrospinal fluid (CSF) or bone marrow aspirate or biopsy, cytopenias (especially thrombocytopenia and leukopenia), and elevated liver enzymes (especially alanine aminotransferase or aspartate aminotransferase). There are two clinically similar but serologically distinct forms of ehrlichiosis: human granulocytic ehrlichiosis (HGE) caused by infection with an Ehrlichia equi-like agent and found primarily in the upper midwest and northeast, and human monocytic ehrlichiosis (HME) caused by Ehrlichia chaffeensis infection and found primarily in the southeastern quadrant of the U.S.
All laboratory testing must be conducted by experienced personnel with appropriate training and include appropriate controls and reagents necessary for accurate etiologic diagnosis.
A clinically compatible case with a single IFA serologic titer ≥1:64 or intracytoplasmic morulae identified in blood, bone marrow or CSF leukocytes
A clinically compatible case that meets the laboratory criteria for diagnosis