ABSTRACT The curve of cumulative cases of individuals infected by COVID-19 shows similar growth to the logistic curve in the period referring to each epidemic “wave”, as each peak of active cases is called. Considering that in pandemic scenarios it is common to seek control measures based on previous experiences, in this paper we model the curve of cumulative cases through a logistic model with infected removal to include the control measures in the dynamics. This model is based on fractional differential equations to also include the memory effect. We study the scenario of the first two “waves” in the analyzed countries: Brazil, China, Italy, and Switzerland. Scenarios with and without control measures are compared, proving the importance of control measures such as isolation. Moreover, this model makes it possible to determine the portion of the population that did not participate in the dynamics of the spread of the disease, as well as to analyze how the number of infected people reduced in each country.

Abstract Ataulfo mango (Mangifera Indica L.) is one of the tropical fruits with highest demand due to its nutritional composition and characteristic flavor. However, losses of processed products, due to the presence of bacteria such as Escherichia coli O157:H7, are usually large. E. coli has been considered one of the 10 major pathogens concerned in foods. The use of high hydrostatic pressure technology in the processing of mango nectar would enable to obtain a safety product. The pathogen Escherichia coli O157:H7 was inoculated at 1x106 CFU/mL in mango nectar. The inoculated samples were then subjected to high hydrostatic pressure (150, 200 and 250 MPa) for 0, 10 and 20 min at 25, 35 and 45 °C. E. coli showed more resistance to high hydrostatic pressure at 25 °C than at 35 or 45 °C. Complete E. coli inactivation was observed at 150 MPa, 35 y 45 °C on day zero (day of treatment) and at 200 MPa, 35 °C on day zero and after 6 days of storage. Identification and quantification of chemical species by solid phase microextraction (SPME) of aromatic profiles of untreated and pressurized mango nectar was carried out. It was observed a reduction with the application of temperature in both, ethanol and α-Pimene concentration, in counterpart β-myrcene and 3-carene were not affected. The pH and total soluble solids showed no significant difference (p<0.05) with the pressure treatments. The treatment by high pressures allowed the complete inactivation of Escherichia coli O157: H7 without causing a negative effect on the aromatic profile of mango nectar.

Resumen El mango Ataulfo (Mangifera Indica L.) es una de las frutas tropicales con mayor demanda debido a su composición nutricional y característico sabor. Sin embargo, existen elevadas pérdidas de productos procesados, debido a la presencia de bacterias como Escherichia coli O157:H7, considerada una de los 10 patógenos de interés mundial presente en los alimentos. El uso de la tecnología de altas presiones hidrostáticas en el procesamiento del néctar de mango permitiría obtener un producto con mayor inocuidad. El patógeno Escherichia coli O157:H7 se inoculó en néctar de mango a una concentración de 1x106 CFU/mL. Las muestras inoculadas se sometieron a la alta presión hidrostática (150, 200 y 250 MPa) por 0, 10 y 20 min, a 25, 35 y 45 °C. E. coli mostró una mayor resistencia a la alta presión a 25 °C en comparación con 35 y 45 °C. La completa inactivación de la bacteria, se observó en las muestras tratadas a 150 MPa con 35 y 45 °C en el día cero (día del tratamiento) y a 200 MPa y 35 °C en el día cero y los siguientes 6 días de almacenamiento. La identificación y cuantificación del perfil aromático se determinó por microextración en fase sólida (SPME). Se observó una disminución en la concentración de etanol y α-pimeno al aplicar mayor temperatura. Con respecto a β-mirceno y 3-careno no hay diferencia significativa respecto al jugo fresco. El pH y los sólidos solubles no presentaron cambios significativos (p<0.05) al aplicarse los tratamientos de alta presión hidrostática. El tratamiento por altas presiones permitió la inactivación completa de Escherichia coli O157:H7 sin causar un efecto negativo sobre el perfil aromático del nectar de mango.