Rocky Mountain Spotted Fever in Mexico: A Call to Action.

Rocky Mountain spotted fever (RMSF) is an ongoing public health crisis in Mexico, particularly in states bordering the United States. The national highest incidence and mortality of RMSF occur in this region, resulting in a case-fatality rate that ranges annually between 10% and 50%, primarily affecting vulnerable groups such as children, elderly adults, and persons living in poverty. Multiple biological, environmental, and social determinants can explain its growing presence throughout the country and how it challenges the health system and society. It is necessary to integrate resources and capacities from health authorities, research centers, and society to succeed in dealing with this problem. Through a scientific symposium, a group of academicians, U.S. health officials, and Mexican health authorities met on November 8-10, 2023, in Hermosillo, Mexico, to discuss the current situation of RMSF across the country and the challenges associated with its occurrence. An urgent call for action to improve national capacity against RMSF in the aspects of epidemiological and acarological surveillance, diagnosis, medical care, case and outbreak prevention, health promotion, and research was urged by the experts. The One Health approach is a proven multidisciplinary strategy to integrate policies and interventions to mitigate and prevent the burden of cases, deaths, and suffering caused by RMSF in Mexico.

Rocky Mountain spotted fever is a neglected tropical disease in Latin America.

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 Mimicking Multisystem Inflammatory Syndrome in Hospitalized Children, Sonora, Mexico.

We describe 5 children who had Rocky Mountain spotted fever (RMSF) and manifested clinical symptoms similar to multisystem inflammatory syndrome in Sonora, Mexico, where RMSF is hyperendemic. Physicians should consider RMSF in differential diagnoses of hospitalized patients with multisystem inflammatory syndrome to prevent illness and death caused by rickettsial disease.

Evaluation of Systemic Inflammation Before and After Standard Anti-tuberculosis Treatment in Patients With Active Pulmonary Tuberculosis and Diabetes Mellitus.

Background Diabetes mellitus (DM) is a common comorbidity of active pulmonary tuberculosis (APTB) that increases the risk of treatment failure during anti-tuberculosis chemotherapy. Evaluating systemic inflammatory response could help determine differences in response to treatment between APTB patients and those with APTB and DM. Methodology To explore changes in systemic inflammation, measured by a set of inflammatory mediators in subjects with APTB and TBDM before and after six months of anti-tuberculosis chemotherapy, 30 APTB and nine TBDM subjects underwent cytokine testing, including interleukin (IL)-6, IL-8, IL-10, interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), and transforming growth factor-beta 1 (TGF-ß1) by enzyme-linked immunosorbent assay, C-reactive protein by nephelometry, and sialic acid by colorimetric assay at baseline and following six months of standard anti-tuberculosis treatment. Sputum smear microscopy or molecular biology (Xpert MTB/RIF) was used for diagnosis, and sputum smear microscopy was performed monthly during the treatment of the patient with pulmonary tuberculosis to evaluate his evolution. Principal component analysis examined changes in the inflammatory status. Results Both groups showed negative sputum smear microscopy in the sixth month after starting anti-tuberculosis chemotherapy. TGF-ß1 was found to be significantly higher in subjects with TBDM before treatment compared to APTB patients (p<0.001), and systemic inflammation continued only in TBDM subjects after treatment (accumulation and persistence of inflammatory mediators like IL-6, IL-8, IL-10, IFN-γ, TNF-α, TGF-ß1, C-reactive protein, and sialic acid in blood). On the other hand, the mediators IFN-γ, C-reactive protein, and total sialic acid were found to be most influential in distinguishing pre- and post-treatment inflammatory response in subjects with APTB without DM. Conclusions Inflammatory mediators analyzed in combination, including IFN-γ, CRP, and total sialic acid, may be useful in evaluating the systemic inflammatory response in subjects with APTB and TBDM before and after anti-tuberculosis treatment. Determining these mediators revealed persistent systemic inflammation in TBDM subjects after six months of standard tuberculosis treatment, despite negative sputum smear microscopy results and good glycemic control. This suggests a need for inflammation-modulating therapies during tuberculosis control. Finally, monitoring sputum smear microscopy results alongside the determination of proposed inflammatory mediators (IFN-γ, CRP, and total sialic acid) are effective in evaluating the response to anti-tuberculosis treatment in APTB subjects without DM, warranting further investigation.

The emergence of Rocky Mountain spotted fever in the southwestern United States and northern Mexico requires a binational One Health approach.

Rocky Mountain spotted fever (RMSF) is an international and quintessential One Health problem. This paper synthesizes recent knowledge in One Health, binational RMSF concerns, and veterinary and human medical perspectives to this fatal, reemerging problem. RMSF, a life-threatening tick-borne disease caused by the bacterium Rickettsia rickettsii, emerged during the first decade of the 21st century in impoverished communities in the southwestern US and northern Mexico. Lack of an index of suspicion, delay in diagnosis, and delayed initiation of antibiotic treatment contribute to fatality. Campaigns targeting dog neutering, restraint to residents' properties, and on-dog and on-premises treatment with acaricides temporarily reduce prevalence but are often untenable economically. Contemporary Mexican RMSF is hyperendemic in small communities and cities, whereas epidemics occur in the western US primarily in small tribal communities. In in both locations, the epidemics are fueled by free-roaming dogs and massive brown dog tick populations. In the US, RMSF has a case fatality rate of 5% to 7%; among thousands of annual cases in Mexico, case fatality often exceeds 30%.1,2 Numerous case patients in US border states have recent travel histories to northern Mexico. Veterinarians and physicians should alert the public to RMSF risk, methods of prevention, and the importance of urgent treatment with doxycycline if symptomatic. One Health professionals contribute ideas to manage ticks and rickettsial disease and provide broad education for the public and medical professionals. Novel management approaches include vaccine development and deployment, acaricide resistance monitoring, and modeling to guide targeted dog population management and other interventions.

Evidencia molecular de Rickettsia ricketsii y Rickettsia felis en garrapatas colectadas en ganado bovino en la costa de Chiapas.

OBJETIVO: Estimar la diversidad de garrapatas, la prevalencia de infestación y tasa de infección de Rickettsia spp. en ganado bovino en la costa del estado de Chiapas. Material y métodos. Se realizó un estudio transversal de octubre de 2021 a marzo de 2022, que incluyó la extracción de garrapatas de 297 vacas pertenecientes a 5 municipios. Se calcularon los índices de diversidad. El diagnóstico de Rickettsia spp en las garrapatas se realizó mediante PCR anida. RESULTADOS: Se encontró una baja diversidad de especies. Las especies Rhipicephalus microplus, Amblyomma cajennense y Rhipicephalus sanguineus hembra adultas fueron positivas a Rickettsia spp. Los municipios de Pijijiapan y Tonalá presentaron la TMI más alta con 7.5 y 7.2%. Conclusión. Este es primer estudio México que reporta infección de Rickettsia spp, en garrapatas colectadas de ganado bovino, lo cual indica un riesgo de salud pública.

Detection of Rickettsia amblyommatis and Rickettsia bellii in ticks collected from pet dogs in peri-urban and rural areas in Yucatan, Mexico.

Rickettsia species are bacteria that may cause multiple diseases in animals and humans, via transmission through multiple arthropod vectors. Routine surveillance of Rickettsia spp. within vectors is critical to determine their presence and risk to mammalian hosts within human populations. Therefore, to better characterize the circulating Rickettsia species in an understudied region we targeted pet dogs to survey. Ticks were collected from pet dogs in three populations of the Yucatan where we tested for the presence of Rickettsia spp. by PCR in metagenomic DNA. In these ticks removed from pet dogs we detected Rickettsia amblyommatis and Rickettsia bellii in Amblyomma auriculatum, Amblyomma ovale and Amblyomma mixtum ticks obtained in a rural community in the Mexican state of Yucatan. This is the first report detecting both species for this state in Mexico, underpinning the importance of more routine surveillance.

Cycle threshold and viral load in SARS-CoV-2-infected patients in Sonora, Mexico.

BACKGROUND: SARS-CoV-2 infection is confirmed with the polymerase chain reaction test. Its positivity is determined by the cycle threshold (Ct), which is inversely proportional to viral load. OBJECTIVE: To describe clinical and epidemiological characteristics of SARS-CoV-2-infected patients according to their viral load estimated by Ct. MATERIAL AND METHODS: Cross-sectional study that included 21,110 confirmed cases, which were stratified according to their viral load: low (Ct > 30), medium (Ct 25-30) and high (Ct < 25). RESULTS: High viral load was identified in 53% of the cases, hospitalization was more common in subjects with medium viral load, and deaths were more prevalent in those with high viral load. Median Ct was lower during the first five days and linearly increased with the days of clinical evolution. There was a higher prevalence of deaths, hospitalizations and ventilatory support in subjects with confirmed SARS-CoV-2 infection who had a medium and high viral load. CONCLUSIONS: The Ct value, correlated with other patient characteristics, can guide the prognosis, as well as the design of interventions that limit the spread of the virus within the population.

ANTECEDENTES: La infección por SARS-CoV-2 se confirma con la prueba de reacción en cadena de la polimerasa. Su positividad se determina mediante el tiempo de ciclado (Ct, cycle threshold), el cual es inversamente proporcional a la carga viral. OBJETIVO: Describir las características clínicas y epidemiológicas de pacientes infectados por SARS-CoV-2 de acuerdo con su carga viral estimada mediante Ct. MATERIAL Y MÉTODOS: Estudio transversal que incluyó 21 110 casos confirmados, los cuales fueron estratificados conforme a su carga viral: baja (Ct > 30), media (Ct 25-30) y alta (Ct < 25). RESULTADO: 53 % de los casos tuvo una carga viral alta, la hospitalización fue más frecuente en sujetos con carga viral media y las defunciones fueron más prevalentes en aquellos con carga viral alta. La mediana del Ct fue más baja durante los primeros cinco días y aumentó linealmente con los días de evolución clínica. Hubo una mayor prevalencia de defunciones, hospitalizaciones y apoyo ventilatorio en sujetos con infección confirmada por SARS-CoV-2 que presentaron carga viral media y alta. CONCLUSIONES: El valor de Ct, correlacionado con otras características del paciente, puede orientar el pronóstico, así como al diseño de intervenciones que limiten la diseminación poblacional del virus.

Tiempo de ciclado y carga viral en pacientes infectados por SARS-CoV-2 en Sonora, México / Cycle threshold and viral load in SARS-CoV-2-infected patients in Sonora, Mexico

Resumen Antecedentes: La infección por SARS-CoV-2 se confirma con la prueba de reacción en cadena de la polimerasa. Su positividad se determina mediante el tiempo de ciclado (Ct, cycle threshold), el cual es inversamente proporcional a la carga viral. Objetivo: Describir las características clínicas y epidemiológicas de pacientes infectados por SARS-CoV-2 de acuerdo con su carga viral estimada mediante Ct. Material y métodos: Estudio transversal que incluyó 21 110 casos confirmados, los cuales fueron estratificados conforme a su carga viral: baja (Ct > 30), media (Ct 25-30) y alta (Ct < 25). Resultado: 53 % de los casos tuvo una carga viral alta, la hospitalización fue más frecuente en sujetos con carga viral media y las defunciones fueron más prevalentes en aquellos con carga viral alta. La mediana del Ct fue más baja durante los primeros cinco días y aumentó linealmente con los días de evolución clínica. Hubo una mayor prevalencia de defunciones, hospitalizaciones y apoyo ventilatorio en sujetos con infección confirmada por SARS-CoV-2 que presentaron carga viral media y alta. Conclusiones: El valor de Ct, correlacionado con otras características del paciente, puede orientar el pronóstico, así como al diseño de intervenciones que limiten la diseminación poblacional del virus.

Abstract Background: SARS-CoV-2 infection is confirmed with the polymerase chain reaction test. Its positivity is determined by the cycle threshold (Ct), which is inversely proportional to viral load. Objective: To describe clinical and epidemiological characteristics of SARS-CoV-2-infected patients according to their viral load estimated by Ct. Material and methods: Cross-sectional study that included 21,110 confirmed cases, which were stratified according to their viral load: low (Ct > 30), medium (Ct 25-30) and high (Ct < 25). Results: High viral load was identified in 53% of the cases, hospitalization was more common in subjects with medium viral load, and deaths were more prevalent in those with high viral load. Median Ct was lower during the first five days and linearly increased with the days of clinical evolution. There was a higher prevalence of deaths, hospitalizations and ventilatory support in subjects with confirmed SARS-CoV-2 infection who had a medium and high viral load. Conclusions: The Ct value, correlated with other patient characteristics, can guide the prognosis, as well as the design of interventions that limit the spread of the virus within the population.

Modeling of Control Efforts against Rhipicephalus sanguineus, the Vector of Rocky Mountain Spotted Fever in Sonora Mexico.

Rocky Mountain spotted fever (RMSF) is a significant health problem in Sonora, Mexico. The tick vector, Rhipicephalus sanguineus, feeds almost exclusively on domestic dogs that, in this region, also serve as the reservoir for the tick-borne pathogen, Rickettsia rickettsii. A process-based mathematical model of the life cycle of R. sanguineus was developed to predict combinations of insecticidal dog collars and long-lasting insecticidal wall treatments resulting in suppression of indoor tick populations. Because of a high burden of RMSF in a rural community near the Sonora state capital of Hermosillo, a test area was treated with a combination of insecticidal dog collars and long-lasting insecticidal wall treatments from March 2018 to April 2019, with subsequent reduction in RMSF cases and deaths. An estimated 80% of the dogs in the area had collars applied and 15% of the houses were treated. Data on tick abundance on walls and dogs, collected during this intervention, were used to parameterize the model. Model results show a variety of treatment combinations likely to be as successful as the one carried out in the test community.

Prevalence of overweight, obesity and central obesity and factors associated with BMI in indigenous yaqui people: a probabilistic cross-sectional survey.

BACKGROUND: The Yaquis are an Indigenous group who inhabit in the state of Sonora in northwestern Mexico. This group has experienced changes in their lifestyle, moving from a traditional lifestyle to a more modern one, resulting in an increase of obesity and its comorbidities. However, few studies have been done in this group. The aim of this study was to determine the prevalence of overweight, obesity and central obesity and to identify the factors associated with body mass index (BMI) in a representative sample of Indigenous Yaqui people from Sonora, Mexico. METHODS: A cross-sectional survey with multistage sampling was conducted among adults (N = 351) with residence in Yaqui traditional villages (Vícam, Pótam, Loma de Guamúchil, Loma de Bácum, Tórim, Ráhum, Huiribis or Belem). Anthropometric measurements were taken to diagnose overweight, obesity and central obesity. Food frequency and physical activity (PA) questionnaires designed for the Yaqui population were applied, as well as sociodemographic and clinical history questionnaires. The factors associated with BMI were assessed using multiple linear regression considering the complex design of the sampling. RESULTS: The prevalence of overweight, obesity and central obesity in the population were 36.5%, 35.0% and 76.0%, respectively. Having higher values of the modernization index (ß = 0.20, p = 0.049) was associated with a higher BMI, while having a higher consumption of a "prudent" dietary pattern (traditional dishes, fruits, vegetables and low-fat dairy) (ß = -0.58, p = 0.009) and performing a greater number of hours per week of vigorous PA (ß = -0.14, p = 0.017) were associated with a lower BMI. CONCLUSIONS: The prevalence of the studied abnormalities is high. The evidence presented in this study suggests that interventions are needed and more research is required to determine the appropriate components of such interventions, in order to meet the needs of the Yaqui people.

Clinical features of patients with Rocky Mountain spotted fever, dengue and chikungunya infection.

INTRODUCTION: Clinical distinction between arbovirus infections and those caused by rickettsia is crucial to initiate appropriate medical treatment. OBJECTIVE: To compare the differences between Rocky Mountain spotted fever (RMSF) and other vector-borne diseases (dengue and chikungunya) with similar clinical presentation, and to identify data that could aid rapid diagnosis of these diseases. METHODS: We evaluated sociodemographic, clinical and laboratory data of 399 patients from five hospitals and clinics of Sonora, Mexico, between 2004 and 2016, with laboratory-confirmed diagnosis of RMSF, dengue, or chikungunya. RESULTS: The RMSF group had the highest lethality (49/63 deaths, 77.8 %), followed by the chikungunya group (3/161, 1.9 %) and the dengue group (3/161, 1.9 %). Clinical differences included the presence of rash, edema, and pruritus; in addition, differences in multiple biomarkers such as platelets, hemoglobin, indirect bilirubin, and serum sodium levels were documented. CONCLUSION: Rash on the palms and soles, edema and absence of pruritus, together with high levels of direct bilirubin and severe thrombocytopenia could be useful indicators to differentiate patients at RMSF advanced stages from those with dengue and chikungunya.

INTRODUCCIÓN: La distinción clínica entre infecciones arbovirales y las provocadas por rickettsias es crucial para iniciar el tratamiento médico apropiado. OBJETIVO: Comparar las diferencias entre fiebre manchada de las montañas rocosas (FMMR) y otras enfermedades transmitidas por vector (dengue y chikungunya) con presentación clínica similar e identificar los datos que pudieran ayudar al diagnóstico rápido de esas enfermedades. MÉTODOS: Se evaluaron datos sociodemográficos, clínicos y de laboratorio de 399 pacientes de cinco hospitales y clínicas en Sonora, México, entre 2004 y 2016, con el diagnóstico confirmado por laboratorio de FMMR, dengue o chikungunya. RESULTADOS: El grupo con FMMR presentó la mayor letalidad (49/63 muertes, 77.8 %), seguido por el de chikungunya (3/161, 1.9 %) y el de dengue (3/161, 1.9 %). Las diferencias clínicas consistieron en la presencia de exantema, edema y prurito; además, se documentaron diferencias en múltiples biomarcadores como plaquetas, hemoglobina, bilirrubina indirecta y niveles de sodio sérico. CONCLUSIÓN: El exantema en palmas y plantas, edema y ausencia de prurito, aunados a niveles altos de bilirrubina directa y trombocitopenia severa pudieran ser indicadores útiles para diferenciar a pacientes con FMMR en etapas avanzadas de aquellos con dengue y chikungunya.

Metabolic syndrome screening using visceral adipose tissue (VAT) from opportunistic MRI locations in a multi-ethnic population.

OBJECTIVE: To determine if visceral adipose tissue (VAT) area measured through MRI can be used opportunistically to assess the presence of cardiometabolic risk factors and compare its performance to simpler adiposity measures. METHODS: A cross-sectional analysis was carried out on a subset of 1683 participants (856 women) from the Adiposity Phenotype Study (mean age=69.2y; range 59.9-77.4). The association of total VAT area (sum of four cross sections, L1-L2, L2-L3, L3-L4, L4-L5) and each location, as well as BMI and body fat % (per SD) with the metabolic syndrome (MetSx) or its components was evaluated through logistic regression analysis. RESULTS: Total VAT can be accurately predicted using all sites evaluated (R2 range=0.82-0.96). In men, VAT did not show a superior association to MetSx compared to BMI in men. However, in women, VAT was consistently superior to BMI and body fat % in its association to MetSx, independent of ethnicity [odds ratio for BMI, body fat %and total VAT area=2.25 (95% CI: 1.93-2.62); 1.66 (95% CI: 1.36-2.03); 6.20 (95% CI: 4.69-8.21) respectively in all women]. Ethnic-specific odds ratios to MetSx in women ranged from 5.38 to 8.63 for total VAT area and 2.12-4.08 for BMI. CONCLUSION: Total VAT area can be accurately predicted from individual VAT regions in men and women and offers superior association to BMI for MetSx in women but not in men for five ethnicities. Therefore, opportunistic screening for elevated VAT area in women may be warranted across multiple ethnic groups.

Increased serum ferritin is associated with oxidized low-density lipoprotein in prediabetes patients: A pilot study.

AIMS: This pilot study aimed to determine if increased serum ferritin (SF) is associated with cardiovascular risk factors in patients with prediabetes. METHODS: Eighteen patients with prediabetes and 36 subjects without prediabetes (control), non-white Hispanic, non-indigenous origin, Mexican mestizo descent were included. Participants had no inflammation, or vascular complications. SF and metabolic markers were evaluated in both groups. RESULTS: SF and oxidized low-density lipoprotein (oxLDL) were increased in prediabetes subjects. Moreover, in prediabetes and control groups as a whole, natural logarithm (ln)-SF correlated with oxLDL and ln-oxLDL/LDL after adjustment for sex, ln-age, ln-fasting plasma glucose (FPG), ln-body mass index, ln-triglyceride (TG), total cholesterol (TC), and high-density lipoproteins. Finally, ln-SF was an independent contributor to ln-oxLDL/LDL ratio in control and prediabetes subjects (ß = 0.2915) after the introduction of potential confounders such as FPG, TC, TG, and hypertension. CONCLUSIONS: The results of this study indicate that hyperferritinemia is associated with oxLDL, considered one of the main cardiovascular risk factors, which allows us to suggest that an increase in SF could contribute to the progression of prediabetes, prior to the appearance of diabetes. Further research is required to establish a causal relationship of iron disruption metabolism in oxLDL generation under prediabetes conditions.

Description of two fatal cases of melioidosis in Mexican children with acute pneumonia: case report.

BACKGROUND: Melioidosis is an infectious disease caused by Burkholderia pseudomallei. In Mexico, the disease is rarely diagnosed in humans and there is no evidence of simultaneous environmental isolation of the pathogen. Here, we describe clinical profiles of fatal cases of melioidosis in two children, in a region without history of that disease. CASE PRESENTATION: About 48 h before onset of symptoms, patients swam in a natural body of water, and thereafter they rapidly developed fatal septicemic illness. Upon necropsy, samples from liver, spleen, lung, cerebrospinal fluid, and bronchial aspirate tissues contained Burkholderia pseudomallei. Environmental samples collected from the locations where the children swam also contained B. pseudomallei. All the clinical and environmental strains showed the same BOX-PCR pattern, suggesting that infection originated from the area where the patients were swimming. CONCLUSIONS: The identification of B. pseudomallei confirmed that melioidosis disease exists in Sonora, Mexico. The presence of B. pseudomallei in the environment may suggest endemicity of the pathogen in the region. This study highlights the importance of strengthening laboratory capacity to prevent and control future melioidosis cases.

Características clínicas de los pacientes con fiebre manchada de las Montañas Rocosas, infección por dengue y chikungunya / Clinical features of patients with Rocky Mountain spotted fever, dengue and chikungunya infection

Resumen Introducción: La distinción clínica entre infecciones arbovirales y las provocadas por rickettsias es crucial para iniciar el tratamiento médico apropiado. Objetivo: Comparar las diferencias entre fiebre manchada de las Montañas Rocosas (FMMR) y otras enfermedades transmitidas por vector (dengue y chikungunya) con presentación clínica similar e identificar los datos que pudieran ayudar al diagnóstico rápido de esas enfermedades. Métodos: Se evaluaron datos sociodemográficos, clínicos y de laboratorio de 399 pacientes de cinco hospitales y clínicas en Sonora, México, entre 2004 y 2016, con el diagnóstico confirmado por laboratorio de FMMR, dengue o chikungunya. Resultados: El grupo con FMMR presentó la mayor letalidad (49/63 muertes, 77.8 %), seguido por el de chikungunya (3/161, 1.9 %) y el de dengue (3/161, 1.9 %). Las diferencias clínicas consistieron en la presencia de exantema, edema y prurito; además, se documentaron diferencias en múltiples biomarcadores como plaquetas, hemoglobina, bilirrubina indirecta y niveles de sodio sérico. Conclusión: El exantema en palmas y plantas, edema y ausencia de prurito, aunados a niveles altos de bilirrubina directa y trombocitopenia severa pudieran ser indicadores útiles para diferenciar a pacientes con FMMR en etapas avanzadas de aquellos con dengue y chikungunya.

Abstract Introduction: Clinical distinction between arbovirus infections and those caused by rickettsia is crucial to initiate appropriate medical treatment. Objective: To compare the differences between Rocky Mountain spotted fever (RMSF) and other vector-borne diseases (dengue and chikungunya) with similar clinical presentation, and to identify data that could aid rapid diagnosis of these diseases. Methods: Sociodemographic, clinical and laboratory data of 399 patients from five hospitals and clinics of Sonora, Mexico, with laboratory-confirmed diagnosis of RMSF, dengue, or chikungunya between 2004 and 2016 were evaluated. Results: The RMSF group had the highest lethality (49/63 deaths, 77.8 %), followed by the chikungunya group (3/161, 1.9 %) and the dengue group (3/161, 1.9 %). Clinical differences included the presence of rash, edema, and pruritus; in addition, differences in multiple biomarkers such as platelets, hemoglobin, indirect bilirubin, and serum sodium levels were documented. Conclusion: Rash on the palms and soles, edema and absence of pruritus, together with high levels of direct bilirubin and severe thrombocytopenia could be useful indicators to differentiate patients at RMSF advanced stages from those with dengue and chikungunya.

The genus Rickettsia in Mexico: Current knowledge and perspectives.

The genus Rickettsia encompasses 35 valid species of intracellular, coccobacilli bacteria that can infect several eukaryotic taxa, causing multiple emerging and re-emerging diseases worldwide. This work aimed to gather and summarise the current knowledge about the genus Rickettsia in Mexico, updating the taxonomy of the bacteria and their hosts by including all the records available until 2020, to elucidate host-parasite relationships and determine the geographical distribution of each Rickettsia species present in the country. Until now, 14 species of Rickettsia belonging to four groups have been recorded in Mexico. These species have been associated with 26 arthropod species (14 hard ticks, three soft ticks, two sucking lice, and seven fleas) and 17 mammal species distributed over 30 states in Mexico. This work highlights the high biological inventory of rickettsias for Mexico and reinforces the need to approach the study of this group from a One Health perspective.

Epidemiology and Clinical Features of Rocky Mountain Spotted Fever from Enhanced Surveillance, Sonora, Mexico: 2015-2018.

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.