Tracking a pandemic using wastewater

Scientists around the world are studying the new coronavirus (SARS-CoV-2) from different perspectives to better understand body-to-body and person-to-person transmission. The goal is to find a cure to neutralize and eliminate it. One of the approaches taken by EPFL and Eawag researchers is to analyze wastewater samples until drug treatments and vaccines are developed, allowing health authorities to detect viruses before the disease is clinically diagnosed. To be able to detect. Tamar Kohn, Head of EPFL’s Institute of Environmental Chemistry (LCE), said:

In collaboration with Christoph Ort of Eawag’s Department of Urban Water Management and Tim Julian of Eawag’s Department of Environmental Microbiology, researchers Coronavirus Can be detected and measured at Wastewater In just a few weeks. The researchers analyzed Lausanne, Zurich, and Lugano samples. This includes Zurich and Lugano samples collected in late February when the first case was recorded in Switzerland. “As a specialist in environmental virology, I was ready to work when the pandemic first arrived in Italy,” says LCE’s Xavier Fernandez Cassi. “It was clear to me that the virus spreads to Switzerland. Given the way interconnected countries exist today, I would have been surprised if not.”

Researchers found traces of the virus in every sample they collected. The concentration of recent samples was so high that it was fairly easy to measure, but not the February sample. “We were delighted to find a signal for only one drainage from Lugano at that time, and another to only six drains from Zurich,” Kohn said. say. Working with colleagues from Eawag, we collected samples for nine wastewater treatment plants in Ticino, two in Zurich and one in Lausanne, for a total of about 800,000 urban dwellers.

The potential impact of this study is so important that another LCE biologist, Cassi and Marie-Hélène Corre, received special permission to work in their EPFL lab during the lockdown. Since the campus was almost unattended, no one else was using the test equipment, so they were particularly efficient at conducting the experiments. However, the new coronavirus, though derived from a known family of viruses, is a zoonotic virus, and researchers therefore needed to pay particular attention. “The main feature of this virus is that it has an envelope. The capsid of the virus is enclosed in a biological membrane,” Corre says. “There are also envelopes for seasonal influenza viruses and HIV.”

Goal: Early warning system

The samples collected since the first case of COVID-19 was reported in Switzerland are a valuable archive. However, the main purpose of this research is not to go back in time, but to develop an early warning system. Ort said: “Samples from 20 large treatment plants spread across Switzerland were able to monitor about 2.5 million people’s wastewater. A quick analysis of the samples showed that diagnostic tests could be carried out, especially during the unlocked period. It may be possible to detect recurrence of infections sooner (about a week earlier) Ort has long been involved in wastewater-based epidemiology, which previously focused on comparing drug use across Europe. “The wastewater is not lying-it reflects what was excreted by the population within a few hours,” he says. The research team utilizes established contacts with local government agencies and wastewater treatment plants.

Track infection trends, not absolute case size

The researchers were able to successfully detect low viral concentrations early in the development of COVID-19 in Switzerland, so they should be able to reconstruct the infection curve. However, it still takes several weeks to analyze more than 300 samples that are currently stored frozen at Eawag and EPFL. The amount of virus that each patient sheds is too variable to use these data to calculate an accurate infection count. However, it is trends that need to be tracked. For example, using samples collected in Lausanne in March and April, researchers were able to roughly track increases in wastewater concentrations of SARS-CoV-2. Corn estimates that the concentration has increased 10 to 100 times.

Complicated way

Despite the researchers’ first successes, they still need to improve their methods further. For example, it is not yet known what percentage of the wastewater viral load will be captured when RNA is extracted after several other steps (filtration and centrifugation). There are also many uncertainties in the subsequent selective amplification process of the target sequence. Only when the amount of uncertainty is reduced can a firm conclusion be drawn about the virus concentration of the original sample.

Coronavirus is unlikely to spread through water or wastewater

Genetic material from the novel coronavirus can be detected in wastewater, but there is currently no evidence to suggest that the pathogen spreads through water or wastewater. Swiss drinking water has excellent microbiological quality and is suitable for consumption during a pandemic.