Rocky Mountain spotted fever

American Dog Tick


Rocky Mountain spotted fever (RMSF) is caused by bacterium Rickettsia rickettsia. It is spread to people through the bite of an infected American Dog Tick (Dermacentor variabilis). RMSF is a rare disease in Connecticut. Because RMSF can result in severe illness, treatment should be started as soon as possible to prevent complications. There are several other rickettsia bacteria that can cause disease in humans, together known as Spotted Fever Rickettsioses (SFR), but these are not spread Connecticut. The best way to prevent RMSF is to prevent tick bites.


About Rocky Mountain spotted fever


Information for Clinicians


Clinical Guidance (CDC)

National Surveillance Case Definition


Connecticut Provider Reporting Information

Reportable Disease Confidential Case Report, PD-23

Connecticut Laboratory Reporting Information

Reportable Laboratory Findings form, OL-15C


Directory of Clinical Testing Services provided by the State Public Health Laboratory

State Public Health Laboratory Contacts – for additional information


RMSF Training Module: Clinical Diagnosis and Treatment for Healthcare Providers (CE)

Tick-borne Diseases of the United States – a Reference Manual for Healthcare Providers


Connecticut Spotted Fever Rickettsiosis Surveillance


In Connecticut, the first case of Rocky Mountain spotted fever (RMSF) was reported in 1965. The Centers for Disease Control and Prevention (CDC) began national surveillance for RMSF in the 1920’s. In 2010, CDC combined cases of RMSF with other rickettsia diseases under a category called Spotted Fever Rickettsiosis (SFR). RMSF is included in the SFR category for national statistics. The Connecticut Department of Public Health (DPH) has maintained surveillance for RMSF for over three decades. DPH uses the CDC surveillance case definition for RMSF, which was first established in 1990. RMSF is rare in Connecticut, and since 1990, an average of 2 RMSF cases (range 0 to 25) have been reported to the DPH annually. From 2009-2018, there have been no reported confirmed cases of RMSF; however, on average, there were 8 probable cases reported annually to the DPH.


Cases of RMSF reported to the DPH from January 1 – December 31, 2019.

4 - Probable


Connecticut Annual Infectious Diseases Statistics




This page last updated 1/14/2020.