Unravelling respiratory syncytial virus outbreaks in Buenos Aires, Argentina: Molecular basis of the spatio-temporal transmission.

Respiratory syncytial virus (RSV) is the main viral cause of hospitalization due to acute lower respiratory tract infections in infants worldwide. Several vaccines against RSV are under research and development, which are about to be approved. We evaluated transmission patterns in different settings to determine age-specific vaccination targets from a viral perspective. We sequenced the G glycoprotein's ectodomain of a constant clinical sampling between two epidemic outbreaks in a limited geographical region and performed phylogeographic analyses. We described a spatio-temporal transmission between local strains, which were originated in the center of the analyzed area and then spread to others. Interestingly, that central area reported the highest population density of the region and also showed overcrowding. This information should be considered by public health systems to evaluate vaccination at all ages in those areas to decrease viral transmission and in lower density populations only susceptible children should be vaccinated.

Caracterización de Cepas de Virus Sincitial Respiratorio en el Gran Buenos Aires y Aspectos de su Diseminación / Characterization of Respiratory Syncytial Virus Strains in the Greater Buenos Aires and Spreading Aspects

INTRODUCCIÓN: El virus sincitial respiratorio (VSR) es el agente viral más frecuente de infecciones respiratorias agudas bajas (IRAB) en la primera infancia y el mayor responsable de las hospitalizaciones en el período invernal. OBJETIVOS: Describir las características de los brotes de VSR en la Zona Sanitaria VI de la provincia de Buenos Aires, establecer la diversidad de las cepas circulantes y realizar el análisis bioinformático y filogeográfico de las secuencias de la glicoproteína G. MÉTODOS: Se estudió a pacientes pediátricos internados con presentación compatible con IRAB durante dos picos epidémicos (2014-2015) en cuatro hospitales. Se recopilaron datos clínicos, demográficos y socio-sanitarios, y se detectaron patógenos virales en aspirados nasofaríngeos de estos pacientes por inmunofluorescencia (IF), obteniéndose la secuencia del gen de la proteína G en los VSR positivos. RESULTADOS: De 1296 casos estudiados, 317 fueron positivos para algún agente viral. De ellos, 266 (84%) fueron VSR positivos. Se hallaron asociaciones significativas entre las poblaciones positivas y negativas para VSR. Una tendencia al hacinamiento y vivienda precaria en los casos VSR positivos fue reflejada en los estudios filogeográficos. CONCLUSIONES: Los datos de firma molecular permitieron trazar orígenes y vías de diseminación del VSR. Esto ayuda a señalar zonas y situaciones de vulnerabilidad, estableciendo la población primaria blanco de planes de vacunación u otras medidas profilácticas.

INTRODUCTION: The respiratory syncytial virus (RSV) is the most frequent viral agent associated to acute lower respiratory infections (ALRIs) in early childhood, being the main responsible for hospitalizations during winter. OBJECTIVES: To describe the characteristics of RSV outbreaks in the Health Area VI of Buenos Aires Province, to establish the diversity of circulating strains and to perform a bioinformatic and phylogeographic analysis of glycoprotein G sequences. METHODS: Pediatric inpatients with ALRI-compatible x|presentation during two epidemic peaks (2014-2015) were studied in four hospitals. Clinical, demographic and socio-sanitary data were collected, viral pathogens were detected by immunofluorescence (IF), and the sequence of the G protein gene was obtained in the positive RSVs. RESULTS: From 1296 cases, 317 were positive for some viral agent and 266 (84%) out of these were RSV positive. Significant associations were found among the positive and negative populations for RSV. A trend towards overcrowding and precarious housing in positive RSV cases was reflected in phylogeographic studies. CONCLUSIONS: The molecular signature data allowed tracing origins and routes of RSV dissemination. This helps identify areas and situations of vulnerability, establishing the primary target population for vaccination plans or other prophylactic measures.