[Retrospective estimation of initial COVID-19 infections in the Santiago Metropolitan Region in Chile]. / Estimación retrospectiva de los casos iniciales de COVID-19 en Santiago Región Metropolitana en Chile.

OBJECTIVE: Estimate daily infections of COVID-19 during the first year of the pandemic in the Santiago Metropolitan Region (SRM) in Chile and Chile that are more realistic than those officially registered. METHOD: Retrospective estimate of daily infections from daily data on COVID-19 deaths, a seroprevalence study, and the REMEDID (Retrospective Methodology to Estimate Daily Infections from Deaths) algorithm. RESULTS: In SRM, it is observed that: 1) the maximum peak of infections was more than double that registered in the official statistics; 2) such peak was reached on May 22 (95% CI: 20-24 May), 2022, that is, 24 days before the official date of the peak of infections; and 3) the first estimated contagion took place on January 28, 2020 (95% CI: January 21 to February 16), that is, 36 days before the official date. In Chile, the situation is similar. During the first wave SRM accounted for 70%-76% of those infected in Chile, while from August 2020 onwards it accounted for 36%-39%. CONCLUSIONS: The official records of COVID-19 infections in SRM and Chile underestimated the real number of positives and showed a delay of about a month in the dynamics of infections. This is not an isolated situation, as it is known to have been the case in other countries as well. However, it is important to have reliable estimates for a correct modeling of the spread of the virus.

Estimación retrospectiva de los casos iniciales de COVID-19 en Santiago Región Metropolitana en Chile / Retrospective estimation of initial COVID-19 infections in the Santiago Metropolitan Region in Chile

Objetivo: Estimar los casos diarios de COVID-19 durante el primer año de pandemia en Santiago Región Metropolitana (SRM) y en Chile con cifras más realistas que las registradas oficialmente. Método: Estimación retrospectiva de los casos diarios a partir de los datos diarios de fallecimientos por COVID-19, un estudio de seroprevalencia y el algoritmo REMEDID (Retrospective Methodology to Estimate Daily Infections from Deaths). Resultados: En SRM se observa que: 1) el pico máximo de contagios fue superior al doble del registrado en las estadísticas oficiales; 2) dicho pico se alcanzó el 22 de mayo de 2020 (IC95%: 20 a 24 de mayo), esto es, 24 días antes de la fecha oficial del pico de contagios; y 3) el primer contagio estimado tuvo lugar el 28 de enero de 2020 (IC95%: 21 de enero a 16 de febrero), esto es, 36 días antes de la fecha oficial. En Chile, la situación es similar. Durante la primera ola, SRM concentró el 70-76% de los infectados de Chile, mientras que a partir de agosto de 2020 solo concentró el 36-39%. Conclusiones: Los registros oficiales de casos de COVID-19 en SRM y Chile infravaloraron el número real de positivos y mostraron un retraso de alrededor de un mes en la dinámica de contagios. Esta no es una situación aislada, ya que se sabe que también ha sido así en otros países. No obstante, es importante disponer de estimaciones fidedignas para una correcta modelización de la expansión del virus.(AU)

Objective: Estimate daily infections of COVID-19 during the first year of the pandemic in the Santiago Metropolitan Region (SRM) in Chile and Chile that are more realistic than those officially registered. Method: Retrospective estimate of daily infections from daily data on COVID-19 deaths, a seroprevalence study, and the REMEDID (Retrospective Methodology to Estimate Daily Infections from Deaths) algorithm. Results: In SRM, it is observed that: 1) the maximum peak of infections was more than double that registered in the official statistics; 2) such peak was reached on May 22 (95% CI: 20–24 May), 2022, that is, 24 days before the official date of the peak of infections; and 3) the first estimated contagion took place on January 28, 2020 (95% CI: January 21 to February 16), that is, 36 days before the official date. In Chile, the situation is similar. During the first wave SRM accounted for 70%–76% of those infected in Chile, while from August 2020 onwards it accounted for 36%–39%. Conclusions: The official records of COVID-19 infections in SRM and Chile underestimated the real number of positives and showed a delay of about a month in the dynamics of infections. This is not an isolated situation, as it is known to have been the case in other countries as well. However, it is important to have reliable estimates for a correct modeling of the spread of the virus.(AU)

Validación de un método de determinación del polisacárido B residual en vesículas de membrana externa de Neisseria meningitidis / Validation of a method of polysaccharide traces determination by HPLC-FL in Outer Membrane Vesicles from N meningitidis

La Cromatografía Líquida de Alta Resolución-Fluorescencia ha resultado ser una herramienta sensible para la detección de trazas en productos farmacéuticos y es utilizada frecuentemente para la cuantificación de algunos polisacáridos de origen bacteriano que poseen ácido siálico como unidad repetitiva. En este trabajo nos planteamos como objetivo establecer y validar el método de HPLC_Fluorescencia, para determinar el contenido de polisacárido B residual en vesículas de membrana externa de Neisseria meningitidis. Para ello se realizó el montaje del método HPLC-FL, utilizando una columna de fase reversa C18 (Ultrasphere ODS, Beckman, USA) y se evaluaron seis lotes de vesículas de membrana externa de diferentes cepas Cu 385/83 y NZ 228. Se demostró que este método permitió la cuantificación de polisacárido B de una forma específica y exacta, y que cumplía con todos los parámetros de validación establecidos para un método de determinación de trazas mediante HPLC(AU)

The High-Resolution Liquid Chromatography-Fluorescence has proven to be a sensitive tool for trace detection in pharmaceuticals and it is frequently used for the quantification of some bacterial polysaccharides that have sialic acid as repeating unit. In this paper we aim at establishing and validating HPLC-fluorescence to determine polysaccharide content of residual B outer membrane vesicles from Neisseria meningitidis. We assembled the HPLC-FL method to the quantification of this residue, using a C18 reverse phase column (ODS UltraSphere, Beckman, USA). We evaluated six lots of outer membrane vesicles from different strains Cu 385/83 and NZ 228. It was demonstrated that the HPLC-FL method allows the quantification of polysaccharide B in a specific and exact manner, and that it complied with the validation parameters for a method for determining trace amounts by HPLC(AU)