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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.

Clinical Description

An illness characterized by fever, chills, headache, photophobia, cough, and myalgia

Laboratory Criteria For Diagnosis

  • Isolation of Chlamydia psittaci from respiratory secretions, OR
  • Fourfold or greater increase in antibody against C. psittaci by complement fixation or microimmunofluorescence (MIF) to a reciprocal titer of greater than or equal to 32 between paired acute- and convalescent-phase serum specimens, OR
  • Presence of immunoglobulin M antibody against C. psittaci by MIF to a reciprocal titer of greater than or equal to 16

Case Classification


A clinically compatible case that is epidemiologically linked to a confirmed case or that has supportive serology (e.g., C. psittaci titer of greater than or equal to 32 in one or more serum specimens obtained after onset of symptoms)


A clinically compatible case that is laboratory confirmed


The serologic findings by complement fixation (CF) also may occur as a result of infection with Chlamydia pneumoniae or Chlamydia trachomatis. The MIF might be more specific for infection with C. psittaci, but experience with and availability of this newer test are more limited.

Related Case Definition(s)