| Abstract |
The disease COVID-19 (Corona Virus Disease 2019), and its causative agent, the SARS-CoV-2 coronavirus, were first recorded in China at the end of 2019 and spread rapidly throughout the planet, causing the COVID-19 pandemic. During the pandemic, the monitoring of the viral load as well as the variants of the coronavirus in wastewater (detection and quantification of SARS-CoV-2 RNA and identification of variants) contributed significantly to the epidemiological surveillance of the COVID-19 disease. During the pandemic, Wastewater-based Epidemiology methodologies quickly evolved into a complementary surveillance tool for COVID-19, while today they are also applied to other public health issues.
While individual-level clinical diagnostic testing for COVID-19 remains ongoing, it alone does not provide a reliable indicator of health risk within community. Given that individuals in various COVID-19 infection states can shed SARS-CoV-2 RNA through feces, WBE was considered a more holistic approach.
Numerous factors, however, can influence RNA recovery from wastewater, hindering its epidemiological significance. Wastewater characteristics such as pH, conductivity, Suspended Solids concentration, etc., as well as seasonal characteristics such as rainfall events, have been found to have possible influence on the recovery of SARS-CoV-2 RNA from wastewater.
Various studies have been carried out in this context and quite a few parameters have been used to interpret and/or normalize the final RNA concentration. Some of the most usual normalization factors include the influent flow rate, the population served by Wastewater Treatment Plants (WWTPs), ammonium and orthophosphate ions, wastewater conductivity and pH, which can also be used for the interpretation of the results.
For this study we received wastewater samples during a broad time frame, which included key societal and pandemic milestones and interventions. Specifically, the study encompasses the period, during which, strict intervention measures (e.g., lockdowns, mandatory face coverings, online lessons, etc.) and their gradual removal were implemented, as well as the start of vaccinations and the emergence of different variants.
From February of 2021 until today, wastewater samples have been collected three times a week from two WWTPs located in the island of Crete, Greece (Chania and Heraklion), which gave us a total of six (6) samples on a weekly basis. Approximately 2-6 L composite samples were collected via autosamplers over a 24-hour period. In total, 781 samples were analyzed for the needs of the current study.
The current study aimed to achieve the following objectives: (1) detect and quantify SARS-CoV-2 genetic material in two WWTPs located in Crete, Greece, (2) establish a potential link between Corona Virus Disease - 19 (COVID-19) cases and SARS-CoV-2 RNA concentrations in wastewater, (3) enhance understanding of the relationship between the physico-chemical characteristics of the wastewater and viral recovery and quantification and (4) assess the impact of in-house and community restrictions during the pandemic, on both human cases and wastewater viral load, considering the effect of mass vaccinations and variants on viral shedding
patterns. The insights gained during this pandemic and the use of WBE is valuable for future management of emerging and challenging public health threats.
|
Collections
