Rocky Mountain Spotted Fever Reemergence in children from Sonora, Mexico. 2004-2012

INTRODUCTION:  Rocky Mountain spotted fever (RMSF) is a re-emerging disease in Sonora, Mexico, spreading from the south of the state to the counties bordering the United States. The disease remains a life-threatening condition, particularly for children living in social deprivation. This study aims to describe RMSF’s epidemiologic and clinical profiles and the medical factors associated with mortality.

METHODS:  We carried out a retrospective analysis of 90 children consecutively hospitalized at the major public pediatric hospital of Sonora, between January 2004 and March 2012. Descriptive statistics and multiple logistic regression were used.

RESULTS:  Over the study period, an increasing trend in the incidence and the case fatality ratio (CFR) was observed. Twenty-six patients died due to RMSF. The overall CFR was 28.9% for the entire period, while the highest CFR (41.9%) occurred in patients less than 4 years of age. Children were hospitalized after a median of 6 days with symptoms, mainly fever (100%), rash involving palms and soles (89%) and headache (75%). A higher proportion (88%) of fatal cases had very low platelet counts (29,403/mm3), and 73% showed serum sodium concentrations <135 mEq/dL. Acute kidney injury was significantly higher in the fatal group than in survivors (69.0% vs. 6.0%, respectively, p<0.001) and remained as the only risk factor that was independently associated with mortality (OR a=28.08, CI95% (6.2, 127.5)).

CONCLUSIONS:  RMSF is a public health problem in Sonora, Mexico; the timely diagnosis and initiation of disease-specific treatment remains as a challenge for the medical community. Acute kidney injury is a life-threatening condition associated with the high fatality rate observed in children