Last reviewed: 29 Oct 2020
Last updated: 13 Mar 2018



History and exam

Key diagnostic factors

  • presence of risk factors
  • abrupt onset of high fever
  • flu-like illness
  • severe headache
  • cough
  • inspiratory crackles, rhonchi, or wheezing
  • hepatomegaly

Other diagnostic factors

  • exanthemas
  • pleuritic chest pain
  • seizures
  • coma
  • chronic fatigue
  • signs of endocarditis or vascular infection (persistent focalised infection)
  • other signs of persistent focalised infection
  • other signs of acute infection

Risk factors

  • exposure to infected animals
  • occupational exposure
  • travel or residency in endemic areas
  • male gender
  • age 30 to 70 years
  • immunosuppression
  • pre-existing cardiac disease
  • pre-existing vasculopathy
  • pregnancy

Diagnostic investigations

1st investigations to order

  • indirect immunofluorescence assay (IFA)
  • PCR
  • FBC
  • CRP
  • LFTs
  • activated partial thromboplastin time (aPTT)
  • IgG anticardiolipin (aCL) antibodies
More 1st investigations to order

Investigations to consider

  • CSF cell count and differential
  • CSF protein
  • CSF glucose
  • CXR
  • transthoracic echocardiography (TTE)
  • transoesophageal echocardiography (TEE)
  • liver ultrasound
  • abdominal CT scan or ultrasound
  • chest CT
  • brain CT
  • 18F-fluorodeoxyglucose (FDG) PET/CT imaging
  • lymph node biopsy
  • immunohistochemistry
  • fluorescence in situ hybridisation (FISH)
More investigations to consider

Treatment algorithm


Division of Infectious Diseases

Uniformed Services University of the Health Sciences




JH declares he has no competing interests. The opinions or assertions contained herein are the private ones of the reviewer and are not to be construed as official or reflecting the views of the Department of Defense, the Uniformed Services University of the Health Sciences, or any other agency of the US Government.

Dr Joshua Hartzell would like to gratefully acknowledge Dr Matthieu Million, Professor Didier Raoult, and Dr Nilmarie Guzman, previous contributors to this monograph. MM and DR are authors of several references used in this monograph. NG declares that she has no competing interests.

Peer reviewersVIEW ALL

Epidemiology Team

Rickettsial Zoonoses Branch

National Center for Zoonotic Vectorborne and Enteric Diseases

Centers for Disease Control and Prevention




JM declares that she has no competing interests.

Clinical Microbiologist

National Influenza Center

Second Department of Microbiology

Aristotle University of Thessaloniki Medical School




DC declares that he has no competing interests.

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