There are approximately 400-1,200 cases of RMSF reported in people in the United States each year. The same seasonal pattern of disease occurs in people as in dogs, and the clinical presentation in people is quite similar to dogs, although the disease tends to be more severe. Following an incubation period of 2-14 days, patients may manifest:

• high fever
• severe malaise, headaches, chills and conjunctival/scleral injection
• hemorrhagic disease - This is much more common in people than in dogs, and the fatality rate in people can approach 25% without therapy (and up to 5% even with antibiotic therapy).
• Neurologic complications occur in approximately two-thirds of patients.
  • RMSF has recently been associated specifically with subsequent Guillain-Barre syndrome in a man from Maryland.

The characteristic petechial rash of RMSF generally begins on the extremities and then spreads over the body. However, the rash does not appear until an average of 3 days after the onset of fever. (Click here for a photo of the RMSF rash)

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