The COVID-19 virus is excreted in fecal matter and the virus genome has been detected in the feces of infected patients, both symptomatic and asymptomatic. It is estimated that 35% of those infected can excrete it, so wastewater monitoring is essential to anticipate the work of clinical doctors, since they anticipate in which sectors of a city it is necessary to test and take public policies in the middle of the pandemic.
It is the work that they carry out María de los Ángeles Marinzalda, Doctor in Biological Sciences; and Ariana Cachi, Graduate in Biotechnology and Doctor in Biochemistry and Molecular Biology.
Both are adjunct researchers at CONICET-FAA and professors and researchers at the UNDEF-Faculty of the Air Force, and researchers at INMAE Córdoba (National Institute of Aeronautical and Space Medicine).
The team of researchers analyzes the residual sewer water from the City of Córdoba and from six towns in the Punilla Valley.
They take weekly samples and make a report that they also make known every 15 days. This allows us to know not only the presence of the wild virus of the Coronavirus, but also the various variants, such as the Delta, whose contagion began in Córdoba: The first case was made known at the end of July.
“We also monitor the sewer lids of the sanitary areas of Córdoba, we take strategically to reflect what happens in the neighborhoods and in these areas, and thus allows us to know if there are areas in which they should test more, and what variant circulates in this zone ”, stated Marinzalda, la Doctor who completed her secondary studies at the María Auxiliadora School in Río Gallegos.
The study that began last year is called “Environmental monitoring of Sars-CoV-2 in sewage waters of the city of Córdoba, Argentina” and was selected in a national call aimed at virus research that receives funds from the National Defense University (UNDEF), the Federal Coordination Program for Science and Technology COVID-19 and the National Agency for its implementation. Promotion of Research, Technological Development and Innovation of the Nation.
“It is a collaborative inter-institutional work. The pandemic did that: That one decides to do something despite the fear that it may imply coming to work with a virus that was not known, but the desire and passion made us do something. It is our grain of sand but the Institute of Virology opened the doors for us, trained us, that is why this is the sum of everything and not just one, ”said Dr. Cachi.
The researchers receive the samples from different wastewater treatment plants. The untreated water is subjected to a centrifugation process that allows the virus and microorganisms to be concentrated in a 5-milliliter sample. There they search for the SARS genome by detecting three genes: N, E and ORS. “With molecular biology it allows us to know if the genome of the virus is present or not. We do not detect the virus in particular, but its genome and RNA ”, explained Marinzalda.
TS: The study makes it possible to anticipate and even detect the various variants of the virus, such as Delta.
Dr. Cachi: When we detect cases in the water, it gives us an alert that an increase in cases is coming and allows us to have a tool to precede an exponential increase in clinical cases one or two weeks.
In the first and second waves, in Ciudad de Córdoba and Valle de la Punilla, we could anticipate one or two weeks what was going to happen clinically. With this alert, measures can be taken from the Ministry of Health to prevent the spread of the virus. Thus, for example, massive tests are carried out in these areas.
In addition to detecting the presence of the virus, we can identify in the waters which variant is circulating in the population.
For example, we have seen that before the second wave we had the circulation of variants that were not of concern and in the second wave we detected the Manaus variant and the United Kingdom variant.
Two weeks ago we detected that the Delta variant began to circulate in the population.
-Does that mean that there is community circulation of the Delta variant?
Dra. Marinzalda: Community circulation means that you cannot find the epidemiological link between the cases, what we know is that it circulates in the population, what we do not know is whether it is in the majority or not. The variant is with the others.
Dr. Cachi: The virus and the variants are in a scenario with people who have already been infected and immunized, with vaccinated people, where the variants are competing for the same thing that the Delta variant wants. It appears in a context with other strains circulating, with the vaccination progressing and measures to continue taking care of ourselves. All of this helps to avoid an explosion of cases.
-Experts indicated that there could be community circulation of the Delta variant in a period of 4 to 8 weeks.
Dra. Marinzalda: We are not Infectologists, but we do say that we must take advantage of those weeks with a strategy to prevent this outbreak. That is why the importance of this study in the world, which is used to monitor the circulation of the variants that gives the tools for strategies, avoid outbreaks, anticipate the increase in cases.
Dr. Cachi: It is a tool for the Ministry of Health to make decisions, to anticipate.
–It is an important study, how long will it continue? The pandemic is not over and is expected to continue for a long time.
It should be adopted as a monitoring mode, beyond research, because we show that this allows us to predict and anticipate the dynamics, how the virus changes and the circulation of different strains.
We have the support of the Ministry of Health of the province for the study and we depend on the financing we have, so we are waiting for an extension, a new call from an agency or at the national level to continue having financial support.
For now, many tests are carried out, but there will come a time when it will decrease and that is where the importance of monitoring the waters increases, because it is like a silent watchdog of what happens, and thus act.