RESUMO
The COVID-19 pandemic has caused a global health crisis, and wastewater-based epidemiology (WBE) has emerged as an important tool to assist public health decision-making. Recent studies have shown that the SARS-CoV-2 RNA concentration in wastewater samples is a reliable indicator of the severity of the pandemic for large populations. However, few studies have established a strong correlation between the number of infected people and the viral concentration in wastewater due to variations in viral shedding over time, viral decay, infiltration, and inflow. Herein we present the relationship between the number of COVID-19-positive patients and the viral concentration in wastewater samples from three different hospitals (A, B, and C) in the city of Belo Horizonte, Minas Gerais, Brazil. A positive and strong correlation between wastewater SARS-CoV-2 concentration and the number of confirmed cases was observed for Hospital B for both regions of the N gene (R = 0.89 and 0.77 for N1 and N2, respectively), while samples from Hospitals A and C showed low and moderate correlations, respectively. Even though the effects of viral decay and infiltration were minimized in our study, the variability of viral shedding throughout the infection period and feces dilution due to water usage for different activities in the hospitals could have affected the viral concentrations. These effects were prominent in Hospital A, which had the smallest sewershed population size, and where no correlation between the number of defecations from COVID-19 patients and viral concentration in wastewater was observed. Although we could not determine trends in the number of infected patients through SARS-CoV-2 concentrations in hospitals' wastewater samples, our results suggest that wastewater monitoring can be efficient for the detection of infected individuals at a local level, complementing clinical data.
Assuntos
COVID-19 , SARS-CoV-2 , Humanos , COVID-19/epidemiologia , Pandemias , Águas Residuárias , Brasil/epidemiologia , RNA Viral , HospitaisRESUMO
Cylindrospermopsis raciborskii is the focus of many studies due to its toxicity and increasing blooms frequency. The comprehension of the factors that might trigger these blooms is fundamental for the maintenance of good freshwater quality. To better understand the autoecology of C. raciborskii and to identify the factors controlling its dominance, general limnological features were evaluated in Pedalinhos reservoir, Brazil. Samplings were performed monthly between 2011 and 2013. Although C. raciborskii is considered a relatively perennial species in the tropics, it presented an interesting nonunimodal variation, with biovolume varying from 0 to c. 30 mm³ L⻹ in short time intervals (< 30 days). These temporal trends allowed the evaluation of the isolated effects of nonclimatic variables. Cylindrospermopsis raciborskii was connected with several variables, but nitrogen was the major determinant of its dynamics. Blooms were observed when dissolved inorganic nitrogen (DIN) was scarce (< 50 µg L⻹), mainly in relation to the availability of phosphorus and total-N (DIN : total-P < 3 and DIN : total-N < 0.04). This paper contributes to establish strategies to avoid C. raciborskii blooms, suggesting that a management in P levels would be not sufficient. It is necessary to consider N availability to avoid its dominance in the reservoir.