Spotted Fever Rickettsiosis
Spotted fever rickettsioses (SFR) are a group of tick-borne rickettsial diseases caused by spotted fever group Rickettsia. The most common reported spotted fever reported in the United States is Rocky Mountain spotted fever (RMSF). RMSF is a rare disease in Connecticut. RMSF is caused by bacterium Rickettsia rickettsii. It is spread to people through the bite of an infected American Dog Tick (Dermacentor variabilis). Because RMSF can result in severe illness, treatment should be started as soon as possible to prevent complications.
There are several other spotted fevers that can cause disease in humans that are reported in the U.S. which include Rickettsia parkeri rickettsiosis, Pacific Coast tick fever, and Rickettsialpox.
Rickettsia parkeri rickettsiosis is caused by Rickettsia parkeri. It is spread to people through the bite of an infected Gulf coast tick, Amblyomma maculatum.
Pacific Coast tick fever is caused by Rickettsia rickettsii subspecies californica (formerly Rickettsia species 364D). It is spread to people through the bite of an infected Pacific Coast tick, Dermacentor occidentalis.
Rickettsialpox is caused by R. akari. It is spread by mites (Liponyssoides sanguineus)carried by the common house mouse.
R. parkeri rickettsiosis, Pacific Coast tick fever, and rickettsialpox are less severe than RMSF, however, it is important to inform your healthcare provider if you have recently been bitten by a tick, exposed to mice, or have been exposed to areas where ticks or mice may be found. The best way to prevent spotted fever illness is to prevent tick bites.
About Rocky Mountain Spotted Fever (CDC)
About Other Spotted Fever Rickettsioses (CDC)
Information for Clinicians
Clinical Guidance for Rocky Mountain Spotted Fever (CDC)
Clinical Guidance for Spotted Fever Rickettsioses (CDC)
National Surveillance Case Definition
Provider Reporting Information
Laboratory Reporting Information
Directory of Clinical Testing Services (State Public Health Laboratory)
State Public Health Laboratory Contacts - for additional information
RMSF Training Module: Clinical Diagnosis and Treatment for Healthcare Providers Continuing Education (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. DPH uses the CDC national surveillance case definition, which was first established in 1990. 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. RMSF is rare in Connecticut, and since 1990, an average of 3 RMSF cases have been reported to the DPH annually.
Connecticut Annual Infectious Diseases Statistics
Last updated 2/5/2025