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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.


  • Human granulocytic ehrlichiosis
  • Human monocytic ehrlichiosis
  • Other or unspecified human ehrlichiosis

Clinical Description

A tick-borne illness characterized by acute onset of fever, headache, myalgia, and/or malaise. Nausea, vomiting, or rash may be present in some cases. Clinical laboratory findings may include thrombocytopenia, leukopenia, and/or elevated liver enzymes. Intracytoplasmic bacterial aggregates (morulae) may be visible in the leukocytes of some patients.

Three categories of confirmed or probable ehrlichiosis should be reported: 1) human ehrlichiosis caused by E. chaffeensis (HME), 2) human ehrlichiosis caused by E. phagocytophila (HGE), and 3) human ehrlichiosis (other or unspecified agent), which includes cases that cannot be easily classified by available laboratory techniques, and cases caused by novel Ehrlichia species such as E. ewingii.

Subtype(s) Case Definition

Case Classification


A clinically compatible illness with either a single positive IFA titer (based on cutoff titers established by the laboratory performing the test) or the visualization of morulae in leukocytes.


A clinically compatible illness that is laboratory-confirmed.

Related Case Definition(s)