Rickettsia rickettsii

microorganism

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Last updated

July 13, 2026

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Rickettsia rickettsii is a bacterium responsible for Rocky Mountain spotted fever (RMSF), a serious and potentially fatal tick-borne illness. This microorganism is part of the Rickettsia genus, which are bacteria that can only reproduce inside host cells.1234

RMSF is characterized by symptoms such as fever, headache, muscle and joint pain, and a distinctive rash that can turn purplish in severe cases. The disease is transmitted to humans through the bite of infected ticks, including the American dog tick, brown dog tick, and wood tick. While historically associated with the Rocky Mountain region, RMSF now occurs across North America and in Central and South America. Early treatment with antibiotics is crucial for recovery and reducing the risk of death.143

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Rocky Mountain spotted fever
…States, caused by the bacterium Rickettsia rickettsii and transmitted by certain species of ticks. Although historically known from the Rocky Mountain region, particularly the U.S. states of Idaho and Montana, today Rocky Mountain spotted fever is most common on the eastern coast of the United States and has been found…
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…States, caused by the bacterium Rickettsia rickettsii and transmitted by certain species of ticks. Although historically known from the Rocky Mountain region, particularly the U.S. states of Idaho and Montana, today Rocky Mountain spotted fever is most common on the eastern coast of the United States and has been found…
Read More