Skip directly to site content Skip directly to search


Centers for Disease Control and Prevention. CDC twenty four seven. Saving Lives, Protecting People
 Search

		Submit


Tickborne Diseases of the United States


Facebook
        Twitter
        LinkedIn
        Syndicate





Rocky Mountain Spotted Fever (RMSF)					minus icon
                Contents
			HomeTick IDOverview of Tickborne DiseasesLyme DiseaseTickborne Relapsing Fever (TBRF)Hard Tick Relapsing FeverAnaplasmosisEhrlichiosisRocky Mountain Spotted FeverRickettsia parkeri RickettsiosisTularemiaBabesiosisHeartland and Bourbon Virus DiseasesColorado Tick FeverPowassan Virus DiseaseTickborne Diseases AbroadTick Bites/PreventionLyme Disease Prophylaxis After Tick Bite					Related Pages
										Agent*Rickettsia rickettsii*RMSF is most often transmitted by the American dog tick in the Eastern, Central and Western United States; by the Rocky Mountain wood tick in the Rocky Mountain states; and by the brown dog tick in the Southwestern United States, along the U.S.-Mexico border. RMSF can be rapidly fatal if not treated within the first 5 days of symptoms. Before tetracycline antibiotics were available, case fatality rates ranged from 20–80%.Child's right hand and wrist displaying the characteristic spotted rash of Rocky Mountain spotted feverWhere FoundSince 2010, cases of RMSF are reported as spotted fever rickettsiosis along with other spotted fevers like *Rickettsia parkeri* rickettsiosis in national surveillance. RMSF has become increasingly common in certain areas of Arizona over the last several years; between 2002-2021 more than 500 cases and 28 fatalities occurred.Incubation Period3–12 daysSigns and SymptomsEarly (1–4 Days)High fever
Severe headache
Malaise
Myalgia
Edema around eyes and on the back of hands
Gastrointestinal symptoms (nausea, vomiting, anorexia)Late (5 Days and Beyond)Altered mental status, coma, cerebral edema
Respiratory compromise (pulmonary edema, ARDS)
Necrosis, requiring amputation
Multiorgan system damage (CNS, renal failure)RashTypically appears 2–5 days after onset of symptoms; approximately 10% of RMSF patients never develop a rash.
Decision to treat should not be based on presence of rash.**Early Rash**
Maculopapular: Small, flat, pink, non-itchy spots (macules) initially appear on the wrists, forearms, and ankles then spread to the trunk and sometimes palms and soles.**Late Rash**
Petechial: Red to purple spots (petechiae) are usually not seen until day 6 or later after onset of symptoms.
Petechial rash is considered a sign of progression to severe disease. Every attempt should be made to begin treatment before petechiae develop.Warning symbol**Confirmation of the diagnosis is based on laboratory testing, but antibiotic therapy should not be delayed in a patient with a suggestive clinical presentation. Antibiotics are more likely to prevent fatal outcome from RMSF if started within the first 5 days of symptoms.**General Laboratory FindingsThrombocytopenia
Elevated hepatic transaminases
Hyponatremia**NOTE:** Laboratory values are often within normal limits in early illness.Laboratory DiagnosisDemonstration of a four-fold rise in IgG-specific antibody titer by indirect immunofluorescence antibody (IFA) assay in paired serum samples. The first sample should be taken within the first 2 weeks of illness and the second should be taken 2 to 4 weeks later.
Detection of DNA in a skin biopsy specimen of a rash lesion by PCR assay or in an acute phase whole blood specimen. Additionally, new pan-*Rickettsia* and *R. rickettsii*-specific PCR assays are available at some local and state health departments.
Immunohistochemical (IHC) staining of organism from skin or tissue biopsy specimen.**NOTE:** Antibody titers are frequently negative in the first 7–10 days of illness. Acute antibody results cannot be independently relied upon for confirmation
**NOTE:** IgM antibodies are less specific than IgG antibodies and are more likely to generate false positives. IgM results alone should not be used for laboratory diagnosis.TreatmentAnaplasmosis, ehrlichiosis, and spotted fever group rickettsioses are treated with doxycycline. Clinical suspicion of any of these diseases is sufficient to begin treatment. **Delay in treatment may result in severe illness and even death**. These regimens may need to be adjusted depending on a person’s age, medical history, underlying health conditions, pregnancy status, or allergies. Consult an infectious disease specialist in cases of pregnancy or life-threatening allergy to doxycycline.

Rocky Mountain Spotted Fever treatment regimen
Age Category
Drug
Dosage
Maximum
Duration (Days)**Adults**
Doxycycline
100 mg twice per day, orally or IV
100 mg/dose
Patients should be treated for at least 3 days after the fever subsides and until there is evidence of clinical improvement. Minimum course of treatment is 5-7 days.**Children weighing <100 lbs. (45.4 kg)**
Doxycycline
2.2 mg/kg per dose twice per day, orally or IV
100 mg/dose**NOTE:** Use doxycycline as the first-line treatment for suspected RMSF in patients of all ages. The use of doxycycline to treat suspected RMSF in children is recommended by both the CDC and the American Academy of Pediatrics Committee on Infectious Diseases. Use of antibiotics other than doxycycline increases the risk of patient death. At the recommended dose and duration needed to treat RMSF, no evidence has been shown to cause staining of permanent teeth, even when multiple courses are given before the age of eight.ReferencesCenters for Disease Control and Prevention. Diagnosis and management of tickborne rickettsial diseases: Rocky Mountain spotted fever and other spotted fever group rickettsioses, ehrlichioses, and anaplasmosis—United States: a practical guide for health care and public health professionals. *MMWR* 2016;65 (No.RR-2).
Demma LJ, Traeger MS, Nicholson WL, et al. Rocky Mountain spotted fever from an unexpected tick vector in Arizona. *N Engl J Med* 2005;353:587–94.
Elghetany MT, Walker DH. Hemostatic changes in Rocky Mountain spotted fever and Mediterranean spotted fever. *Am J Clin Pathol* 1999;112:159–68.
Holman RC, Paddock CD, Curns AT, et al. Analysis of risk factors for fatal Rocky Mountain spotted fever: evidence for superiority of tetracyclines for therapy. *J Infect Dis* 2001;184:1437–44.
Jay R, Armstrong PA. Clinical characteristics of Rocky Mountain spotted fever in the United States: A literature review. *J Vector Borne Dis*. 2020 Apr-Jun;57(2):114-120.
Kirkland KB, Wilkinson WE, Sexton DJ. Therapeutic delay and mortality in cases of Rocky Mountain spotted fever. *Clin Infect Dis* 1995;20:1118–21.
Massey EW, Thames T, Coffey CE, et al. Neurologic complications of Rocky Mountain spotted fever. *South Med J* 1985;78:1288–90, 1303.
McQuiston JH, Wiedeman C, Singleton J, et al. Inadequacy of IgM antibody tests for diagnosis of Rocky Mountain Spotted Fever. *Am J Trop Med Hyg*. 2014 Oct;91(4):767-70.
Paddock CD, Alvarez-Herandez G. *Rickettsia rickettsii* (Rocky Mountain spotted fever). In: *Principles and Practice of Pediatric Infectious Diseases*. 5th ed. Philadelphia, PA: Elsevier; 2017. p. 952-957.
Regan JJ, Traeger MS, Humpherys D, et al. Risk factors for fatal outcome from Rocky Mountain spotted fever in a highly endemic area—Arizona, 2002–2011. *Clin Infect Dis* 2015;60:1659–66.
Smithee L, et al. Public health reporting and national notification for spotted fever rickettsiosis (including Rocky Mountain spotted fever). Council of State and Territorial Epidemiologists, Infectious Diseases Committee, 2009 Position Statement. [PDF – 11 pages]
Todd SR, Dahlgren FS, et al. No visible dental staining in children treated with doxycycline for suspected Rocky Mountain spotted fever. *J Pediatr* 2015;166(5):1246-51
Traeger MS, Regan JJ, Humpherys D, et al. Rocky Mountain spotted fever characterization and comparison to similar illnesses in a highly endemic area—Arizona, 2002–2011. *Clin Infect Dis* 2015;60:1650–8.Top of Page
									PrevEhrlichiosis
			NextRickettsia parker...
							
					
						Page last reviewed:  August 5, 2022					Content source: 	Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases (NCEZID), Division of Vector-Borne Diseases (DVBD) homeTickborne Diseases of the United StatesTick IDOverview of Tickborne DiseasesLyme DiseaseTickborne Relapsing Fever (TBRF)Hard Tick Relapsing FeverAnaplasmosisEhrlichiosisRocky Mountain Spotted Fever*Rickettsia parkeri*RickettsiosisTularemiaBabesiosisHeartland and Bourbon Virus DiseasesColorado Tick FeverPowassan Virus DiseaseTickborne Diseases AbroadTick Bites/PreventionLyme Disease Prophylaxis After Tick Bite


About CDC
					Contact Us
					800-232-4636
 Facebook Twitter Instagram LinkedIn Youtube Pinterest Snapchat
 CONTACT CDC
				Contact Us
							Call 800-232-4636
							Email Us
			ABOUT CDC
				About CDC
							Jobs
							Funding
			POLICIES
				Accessibility
							External Links
							Privacy
							Policies
							No Fear Act
							FOIA
							OIG
							Nondiscrimination
							Vulnerability Disclosure Policy
			CONNECT WITH US
				Facebook
								Twitter
								Instagram
								LinkedIn
							Youtube
								Pinterest
								Snapchat
								Email
			LANGUAGES
				Español
							繁體中文
							Tiếng Việt
							한국어
							Tagalog
							Русский
							العربية
							Kreyòl Ayisyen
							Français
							Polski
							Português
							Italiano
							Deutsch
							日本語
							فارسی
							English


U.S. Department of Health & Human Services
			Accessibility
			External Links
			Privacy
			Policies
			No Fear Act
			FOIA
			Nondiscrimination
			OIG
			Vulnerability Disclosure Policy
			USA.gov


Exit Notification / Disclaimer Policy Close
 Links with this icon  indicate that you are leaving the CDC website. The Centers for Disease Control and Prevention (CDC) cannot attest to the accuracy of a non-federal website.
				Linking to a non-federal website does not constitute an endorsement by CDC or any of its employees of the sponsors or the information and products presented on the website.
				You will be subject to the destination website's privacy policy when you follow the link.
				CDC is not responsible for Section 508 compliance (accessibility) on other federal or private website. Website Disclaimers
 Cancel Continue