The presence of SARS-CoV-2 RNA traces in the faeces of COVID-19 patients has opened up two new avenues of research to combat the disease. One of these research lines focuses on determining whether the faecal-oral route could be a relevant vector in the transmission of COVID-19. The other research line seeks to establish an early warning system through the surveillance of genetic material present in the wastewater collected from urban areas and using this as an indicator of the degree to which the population is infected by the disease. The IATA-CSIC and CEBAS-CSIC research teams have been working on this second line of research since early March, prior to the declaration of the State of Alarm in Spain.
On March 11, 2020, the World Health Organisation declared the global SARS-CoV-2 pandemic, which causes the illness known as COVID-19. This virus, which belongs to the coronavirus family, is transmitted amongst humans mainly through respiratory secretions. However, SARS-CoV-2 has also been detected in the faeces and urine of COVID-19 patients and asymptomatic carriers (He et al., 2020; Pan et al., 2020; Woelfel et al., 2020; Sun et al., 2020). Despite the fact that the quantity of genetic material secreted can vary from 102 to 108 RNA copies per gram (Pan et al., 2020; Woelfel et al., 2020), the faecal-oral route of transmission has yet to be confirmed.
The presence of this genetic material in faeces brought attention to the possible presence of SARS-CoV-2 RNA in wastewater. Previously, other diseases caused by enteric viruses, such as the hepatitis E virus, norovirus and poliovirus, had been studied by searching for their genetic material in wastewater. A number of research studies worldwide have now detected SARS-CoV-2 RNA in wastewater (Ahmed et al., 2020; Lodder, et al., 2020; Medema et al., 2020; Randazzo et al., 2020; Wu et al., 2020; Wurtzer et al., 2020). These studies suggest that monitoring SARS-CoV-2 genetic material in wastewater could be a non-invasive early warning tool to evaluate COVID-19 infection status and trends in a population, as well as an instrument to adjust the response of public health services.
Epidemiological surveillance in the Region of Murcia
The research being carried out commenced in the first week of March and focuses on the analysis of the influent of six wastewater treatment plants in the Region of Murcia, which represents approximately half of all the wastewater generated in this region. Analysis of wastewater in Murcia began even before the declaration of the State of Alarm in Spain and some of the plants treat the wastewater from districts where no positive cases of COVID-19 had been registered by health authorities up to that time. Indeed, in three of the districts where samples were taken, the first cases of people affected by the disease were declared between 12 and 16 days after the sample-taking began. However, the wastewater analysis revealed that SARS-CoV-2 RNA was already in circulation weeks prior to the confirmation of the first case of COVID-19 in these districts.
Walter Randazzo1,2, Pilar Truchado3, Enric Cuevas-Ferrando2, Pedro Simón Andreu4, Ana Allende3, Gloria Sánchez2*
1Department of Microbiology and Ecology, University of Valencia
2Department of Preservation and Food Safety Technologies, Institute of Agrochemistry and Food Technology, IATA-CSIC
3Research Group on Quality, Safety and Bioactivity of Plant Foods, Department of Food Science and Technology, CEBAS-CSIC
Published in: FuturENVIRO Nº 69 April-May 2020