[ad_1]
Researchers used DNA testing technology to detect traces of the SARS-CoV-2 virus behind Covid-19 in wastewater streams to predict and prevent outbreaks locally.
Wastewater analysis can be a useful method to study the behavior of people living in a specific region. For example, a European to study conducted in 2014 examined the presence of illicit drugs in wastewater, providing information on the timing and frequency of use of different substances.
As the pandemic hit cities around the world, local authorities around the world have sprung into action with different strategies to control the spread of the virus. These included contact tracing, targeted lockdowns, and mandatory quarantines, among others. Unlike all of these strategies that chase the spread of the virus, sewer testing allows scientists to predict infection hot spots in advance. This is because infected people may pass the virus in their stool a few days before symptoms appear, if at all.
Find viruses in wastewater
The process of finding SARS-CoV-2 in wastewater far exceeds the proverbial challenge of finding a needle in a haystack. If you weighed all the SARS-CoV-2 viruses in infected individuals around the world, they would total about 1kg. Only a fraction of it ends up in wastewater, millions of cubic meters of which are sent to wastewater treatment plants. For wastewater surveillance to be effective in predicting regional outbreaks, authorities must detect the virus when only a few people exceed it, making the task even more difficult.
Fortunately, the biotech industry has a toolkit for this task. This includes different viral concentrating techniques originally developed to detect enteric viruses – the most common cause of gastroenteritis worldwide – in wastewater. Among other technologies, companies and research groups are using direct electronegative membrane RNA extraction, ultrafiltration, ultracentrifugation and polyethylene glycol precipitation to extract SARS-CoV-2 genetic material from wastewater. untreated.
In response to widespread interest in the epidemiology of wastewater, global manufacturers of molecular tests, such as Qiagen, Thermo Fisher Scientific, and Promega, have added coronavirus wastewater test kits to their portfolios. Promega offers a high throughput kit that uses magnetic beads to extract genetic material from the sample.
“The whole process takes less than two hours and is scalable and adaptable. Agnieszka Dobrogowski, Product Manager at Promega, told me.
Quantify the virus
Once the presence of the virus is confirmed in a wastewater sample, the next step is to amplify the nucleic content for quantification. This step can be performed using quantitative PCR – a version of the PCR technique also used in Covid-19 diagnostic tests. Although this technology is well established, it often does not provide the sensitivity required to accurately quantify small amounts of DNA.
The French biotech C4Diagnostics is developing in vitro diagnostic tests for infectious diseases. After demonstrating the early detection of SARS-CoV-2 in wastewater from nursing homes in France, the startup is now partnering with businesses and local communities to monitor the virus in their wastewater.
“In a building of 100 people, it only takes one person infected with the virus to detect a positive signal in the wastewater. This is how sensitive technology is ”, said Younes Lazrak, CEO and co-founder of C4Diagnostics. “With this information in hand, you can then trace who is infected with individual tests and take appropriate action to prevent the spread of the virus.”
“We took part in a major monitoring campaign in France, from September to October 2020, where, every week, we tested the wastewater from 78 nursing homes for the elderly. This study has shown that the detection of SARS-CoV-2 in wastewater is a warning of future Covid-19 epidemics and allows the implementation of a targeted prevention strategy. “
The final piece of the puzzle is to estimate the magnitude of infected individuals in an area from the amount of virus in the sewage samples. Silvia Bofill-Mas is a virologist at the University of Barcelona who has been following viruses in wastewater for almost two decades as part of the Catalan Network for Surveillance of SARS-CoV-2 in Wastewater. His team noticed a strong correlation between daily virus loads and number of cases in the area one week after collection.
In order to make sure their measurements are accurate, the team uses other viruses as a check.
“The best way is to add a virus you know to your sample and try to detect it at the end of the process to make sure you’ve done it right. You should add a virus as similar as possible to SARS-CoV-2 because the structure of the virus will influence the efficiency with which you retrieve them from the environment ”, Bofill-Mas explains.
“Since SARS-CoV-2 is an enveloped virus, you need to work with an enveloped surrogate as similar as possible to SARS-CoV-2, preferably an animal or bacterial virus that can be easily handled in the lab. “
A challenge in quantification is that it is not yet clear if and how the properties of wastewater and sewer conditions affect the survival of the virus. In addition, there is no reason to believe that all patients excrete similar amounts of the virus in the stool. However, this variability is only of concern when there are very few cases. As the number of cases increases, the variation becomes average. And while the exact number of people infected cannot be safely estimated, detecting increasing levels of SARS-CoV-2 still allows scientists to predict local infection hot spots.
As Europe faces new concerns due to the rapid spread of the delta variant, which is quickly becoming the dominant variant in many countries, the wastewater epidemiology measures put in place over the past year could help predict and prevent waves of infections.
“More importantly, this technology tells us not only about people with clinical symptoms, but also asymptomatic people. In addition, it may be useful to study which variants are prevalent within a population in a single analysis without having to perform individual tests ”, said Bofill-Mas.
Source link
