Prognosis

Patients who receive therapy within the first week of illness will generally show signs of improvement, including defervescence, within 72 hours of initiating doxycycline therapy; lack of improvement suggests the need to search for an alternative diagnosis.[1][14]

Mortality

Most patients will recover completely, especially if appropriate antibiotic therapy is initiated within the first 5 days of illness. In the pre-antibiotic era, roughly 30% of patients with Rocky Mountain spotted fever (RMSF) died. With improvements in supportive care and the development of effective antibiotics, the case fatality rate has steadily declined. Since 2001, <1% of reported RMSF cases in the US have had fatal outcomes.[2][3]​​ However, this decline may be partially due to changes in diagnostic and reporting practices; clinical reviews suggest 5% to 10% of RMSF cases are fatal.[3]​​[5]​ A more virulent strain of RMSF has been reported in Mexico, with a case fatality rate of 40%, including in appropriately treated cases.[20]

The most significant risk factor for death from RMSF is delay in initiation of appropriate antimicrobial therapy.

An analysis of reported RMSF cases from 1999 to 2007 found that mortality was increased among children aged 5 to 9 years, adults aged 70 years and older, American Indians, immunosuppressed people, and people presenting during the period from 1 March through to 31 May.[27]​ Older studies have also linked mortality to factors that lead to delays in (or omission of) therapy, such as lack of known history of tick attachment; presentation without headache; delayed presentation of the rash, or delay in its recognition; and presentation with a first symptom other than fever, rash, or headache.[15]​​[28]​​[29]​​

Morbidity

Roughly 10% to 15% of surviving patients are discharged from hospital with residual, and in some cases permanent, neurological deficits.[1] Neurological complications include cognitive impairment, paresis, hearing loss, blindness, neuropathy, and cortical brain dysfunction. Non-neurological sequelae occur less commonly and are principally related to cutaneous necrosis, which can require skin grafting or amputation of affected digits or limbs.[1][14][30]​​ In children, independent risk factors for adverse neurological outcomes include coma and requirement for fluid boluses and/or inotropic support.[14]

Use of this content is subject to our disclaimer