Social and environmental determinants of Rocky Mountain spotted fever at the census-tract level in the cities of Hermosillo and Obregon in Sonora, Mexico.

Rocky Mountain Spotted Fever (RMSF) is a disease caused by the Rickettsia rickettsii bacteria, transmitted by the bite of infected Ixodidae hard ticks. The incidence of RMSF in Sonora, Mexico is one of the highest at the national level, with fatality rates above 30%. To better understand the spatial distribution of the disease in endemic urban areas of Mexico, we explored how physical and social determinants relate with its geographic patterns. We describe the incidence distribution of RMSF at the census tract level in two cities of Sonora, Mexico, and examine the correlation of the cumulative incidence with an index of social marginalization (ISM), as well as with land surface temperature. Overall, a heterogeneous spatial distribution of RMSF with hot spots randomly dispersed across both cities was observed. Furthermore, there were hot spots characterized by a high incidence of RMSF, a high ISM, and a land surface temperature above 31.6° C. Our findings show that the spatial analysis of physical and social determinants can be used to identify hot spots of RMSF at the census-tract level to which specific measures of prevention and control can be directed.