Rocky Mountain spotted fever (RMSF), caused by Rickettsia rickettsii, is a severe and potentially fatal tick-borne disease. In 2015, Mexico issued a declaration of epidemiologic emergency in response to ongoing outbreaks of RMSF in northern Mexico. Sonora state is one of the most heavily impacted states in Mexico, with historic case fatality rates (CFRs) of 18%. We summarized data from enhanced surveillance to understand demographic, clinical, and treatment factors associated with the high mortality. We conducted a retrospective review of confirmed and probable RMSF cases reported to the General Directorate of Health Promotion and Disease Prevention in Sonora. A case of RMSF is defined as fever (> 38.5°C), plus two symptoms, and epidemiologic criteria. A confirmed case requires laboratory evidence. During 2015–2018, a total of 510 cases of RMSF were reported; 252 (49%) were in persons aged ≤ 18 years. Case fatality rate was 44% (n = 222). Older age and being confirmed by PCR were associated with fatal outcome (P-value < 0.01). The mean time from onset of symptoms to treatment with doxycycline was 7.9 days (SD ± 5.5). Hot spot analysis revealed neither areas of inordinately high nor low incidence, rather clusters of disease in population centers. The CFR for RMSF in Sonora remains high, and a large proportion of cases are seen in persons aged ≤ 18 years. Whereas previously children experienced a disproportionately high CFR, interventions have reversed this trend. Disease clusters in urban nuclei, but location remains a predictor of fatal outcome.

We report Rickettsia parkeri and Candidatus Rickettsia andeanae in ticks of the Amblyomma maculatum group collected from dogs in Sonora, Mexico. Molecular characterization of these bacteria was accomplished by DNA amplification and sequence analysis of portions of the rickettsial genes gltA, htrA, ompA, and ompB.

Rocky Mountain spotted fever (RMSF), a severe and extraordinarily lethal infectious disease, has emerged as a widespread public health crisis among predominantly vulnerable populations in several countries of Latin America, particularly evident in northern Mexico. Historically, RMSF has gained less attention than many other tropical infectious diseases, resulting in insufficient allocations of resources and development of capabilities for its prevention and control in endemic regions. We argue that RMSF fulfills accepted criteria for a neglected tropical disease (NTD). The relative neglect of RMSF in most Latin American countries contributes to disparities in morbidity and mortality witnessed in this region. By recognizing RMSF as an NTD, an increased public policy interest, equitable and more appropriate allocation of resources, scientific interest, and social participation can ameliorate the impact of this potentially treatable disease, particularly in vulnerable populations. Rocky Mountain spotted fever (RMSF), a severe and extraordinarily lethal infectious disease, affects predominantly vulnerable populations in several countries of Latin America. The pathogen, Rickettsia rickettsii, is transmitted to humans through the bite of infected hard ticks from the family Ixodidae. When RMSF is not diagnosed or treated promptly, it often results in life-threatening disease and can be rapidly fatal in as many as 30% to 60% of patients. Among survivors, RMSF can result in long-term sequelae, including permanent cognitive deficits and amputations resulting from gangrene of extremities and appendages. Hyperendemic levels of RMSF, witnessed currently in multiple states across northern Mexico, arises from a complex interaction of zoonotic, environmental, and social determinants that pose enormous challenges to health systems and public policies. These same determinants also exist in most Latin American countries, which place the region at great risk for devastating levels of disease. Historically, RMSF has gained far less attention than many other tropical infectious diseases of equivalent or lesser magnitude, resulting in insufficient allocation of resources and limited efforts for its prevention and control. The neglect of RMSF in most Latin American countries contributes to broadening disparities in morbidity and mortality across this region that involve predominantly persons living in poverty, children, and to an increasing degree, pregnant women. Formal recognition of RMSF as a neglected tropical disease is an important step toward reducing the public health burden created by this disease, fostering political and scientific interest and increasing financial resources for the implementation of medical and sanitary interventions.

We present a series of four pregnant women with Rocky Mountain spotted fever (RMSF) that occurred in Sonora, Mexico, during 2015–2016. Confirmatory diagnoses were made by polymerase chain reaction or serological reactivity to antigens of Rickettsia rickettsii by using an indirect immunofluorescence antibody assay. Each patient presented with fever and petechial rash and was treated successfully with doxycycline. Each of the women and one full-term infant delivered at 36 weeks gestation survived the infection. Three of the patients in their first trimester of pregnancy suffered spontaneous abortions. RMSF should be suspected in any pregnant woman presenting with fever, malaise and rash in regions where R. rickettsii is endemic.