Rocky Mountain Spotted Fever

What is Rocky Mountain spotted fever?

Rocky Mountain spotted fever (RMSF) is the most severe tick-borne rickettsial illness in the United States. This disease is caused by infection with the bacterial organism Rickettsia rickettsii.

How do people get Rocky Mountain spotted fever?

The organism that causes Rocky Mountain spotted fever is transmitted by the bite of an infected tick. The American dog tick (Dermacentor variabilis) and Rocky Mountain wood tick (Dermacentor andersoni) are the primary athropods (vectors) which transmit Rocky Mountain spotted fever bacteria in the United States. The brown dog tick Rhipicephalus sanguineus has also been implicated as a vector as well as the tick Amblyomma cajennense in countries south of the United States.

What are the symptoms of Rocky Mountain spotted fever?

Patients infected with R. rickettsii usually visit a physician in their first week of illness, following an incubation period of about 5-10 days after a tick bite. The early clinical presentation of Rocky Mountain spotted fever is often nonspecific and may resemble many other infectious and non-infectious diseases. Initial symptoms may include fever, nausea, vomiting, muscle pain, lack of appetite and severe headache. Later signs and symptoms include rash, abdominal pain, joint pain, and diarrhea. Three important components of the clinical presentation are fever, rash, and a previous tick bite, although one or more of these components may not be present when the patient is first seen for medical care. Rocky Mountain spotted fever can be a severe illness, and the majority of patients are hospitalized.

In the United States, where do most cases of Rocky Mountain spotted fever occur?

Rocky Mountain spotted fever is a seasonal disease and occurs throughout the United States during the months of April through September. Over half of the cases occur in the south-Atlantic region of the United States (Delaware, Maryland, Washington D.C., Virginia, West Virginia, North Carolina, South Carolina, Georgia, and Florida). The highest incidence rates have been found in North Carolina and Oklahoma. Although this disease was first discovered and recognized in the Rocky Mountain area, relatively few cases are reported from that area today.



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