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Rocky Mountain spotted fever

Last reviewed: 28 Oct 2023
Last updated: 05 Apr 2023



History and exam

Key diagnostic factors

  • known recent tick exposure or bite
  • triad of fever, rash, and history of tick exposure
  • triad of fever, rash, and headache
  • fever
  • rash
  • headache
  • nausea/vomiting
  • myalgia
  • altered mental status
More key diagnostic factors

Other diagnostic factors

  • abdominal pain
  • residence in or recent exposure to rural area
  • diarrhea
  • conjunctivitis
  • lymphadenopathy
  • peripheral edema
  • meningismus
  • splenomegaly
  • hepatomegaly
  • jaundice
  • seizures
  • shock
  • coma
Other diagnostic factors

Risk factors

  • illness onset in spring or summer
  • returned travelers from an endemic area
  • recent (within 2 weeks) outdoor exposure
  • known antecedent tick bite
  • exposure to dogs or pets that spend time outdoors
More risk factors

Diagnostic investigations

1st investigations to order

  • CBC
  • serum electrolytes and blood urea nitrogen (BUN)
  • LFTs
  • indirect immunofluorescent antibody (IFA)
  • blood culture
More 1st investigations to order

Investigations to consider

  • complement fixation
  • latex agglutination
  • indirect hemagglutination
  • microagglutination
  • enzyme immunoassay
  • lumbar puncture
  • convalescent serology
  • chest x-ray
  • abdominal CT scan
  • immunohistochemistry
  • polymerase chain reaction
More investigations to consider

Treatment algorithm


suspected Rocky Mountain spotted fever



Christopher A. Ohl, MD

Professor of Medicine

Section on Infectious Diseases

Wake Forest School of Medicine




CAO declares that he has no competing interests.


Professor Christopher A. Ohl would like to gratefully acknowledge Dr Steven C. Buckingham, a previous contributor to this topic. SCB is an author of several references cited in this topic. We were made aware that Dr Steven C. Buckingham is now deceased.

Peer reviewers

Mary Anne Jackson, MD


Section of Pediatric Infectious Diseases

Children's Mercy Hospital and Clinics

Professor of Pediatrics

University of Missouri-Kansas City School of Medicine

Kansas City



MAJ is an author of several references cited in this topic.

  • Rocky Mountain spotted fever images
  • Differentials

    • Other rickettsial diseases
    • Meningococcemia
    • Ehrlichiosis
    More Differentials
  • Guidelines

    • Tickborne diseases of the United States: a reference manual for health care providers
    • CDC Health information for international travel (the Yellow Book): rickettsial diseases (including spotted fever & typhus fevers rickettsioses, scrub typhus, anaplasmosis, and ehrlichioses)
    More Guidelines
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