The results of wastewater monitoring can also serve as an early detection and warning tool in the event that the coronavirus returns. So far, the problem is that there are not enough reagents for research, experts say.
More than a dozen research groups around the world have begun to study wastewater for the presence of traces of the new coronavirus. In their opinion, this may be one of the ways to assess the total number of infected in a particular community, since it is simply impossible to screen all people for coronavirus infection. The technique can also be used to detect the coronavirus before people show symptoms, according to scientists. To date, scientists have already found traces of this virus in wastewater in the Netherlands, the United States and Sweden.
Analyzing wastewater - waste water that passes through a sewer network and into treatment plants - is one way researchers can track infections that are excreted in urine and faeces, such as SARS-CoV-2.
A single wastewater treatment plant receives wastewater from about a million people, said Gertjan Medema, a microbiologist at the KWR Water Research Institute in Nieuwegein, the Netherlands. Analysis of wastewater in such volumes makes it possible to more accurately assess the extent of the spread of coronavirus infection than testing people, because monitoring of wastewater makes it possible to take into account those cases when people were not tested for coronavirus infection, and when people had only mild symptoms of the disease. Medema has discovered the genetic material of SARS-CoV-2 - the RNA of the virus - in samples taken at several wastewater treatment plants in the Netherlands. "Health authorities only see the tip of the iceberg."
According to scientists, in order to accurately assess the spread of infection in a particular community, based on wastewater samples, it is necessary to find out exactly how much RNA of the virus is excreted in the feces and calculate the number of infected people in this community based on data on the concentration of RNA of the virus in wastewater samples. water.
In addition, scientists will need to make sure that they are analyzing representative samples of water containing human excreta, and not random samples, and that their tests detect low concentrations of the virus RNA, scientists representing the Queensland Alliance of Environmental Health Experts said (The Queensland Alliance for Environmental Health Sciences in Australia is a research center that advises the country's government on environmental sanitation issues. It is very important, they said, that wastewater monitoring - if it is started on a significant scale - does not drain the resources needed to conduct tests on humans.
Part of the effort to track the spread of the virus has been hampered by the closure of universities and laboratories, and limited supplies of reagents for research - the same reagents used in clinics that are no longer available, according to Kyle Bibby. Bibby, an environmentalist at the University of Notre Dame in Indiana. “We do not want to exacerbate the global resource shortage,” he said.
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Early evidence of discovery
Infection control measures, such as social distancing, are likely to tackle the current pandemic, but the virus could return once these measures are lifted. Continuous monitoring of wastewater can serve as a non-invasive early warning tool, said Ana Maria de Roda Husman, an infectious disease expert at the National Institute for Public Health and the Environment in Bilthoven., Netherlands. The institute previously investigated wastewater to monitor outbreaks of norovirus, antibiotic-resistant bacteria, poliovirus and measles.
A team of experts led by Husman found traces of SARS-CoV-2 in the sewage at Schiphol Airport in Tilburg just four days after the first case was confirmed in the Netherlands. Scientists now plan to investigate wastewater in the capitals of all 12 provinces of the Netherlands, as well as in other cities where no confirmed cases have been recorded so far. A group of scientists led by Medema detected coronavirus RNA in the sewage of the city of Amersfoort even before the first cases of infection were confirmed there.
Studies have shown that traces of SARS-CoV-2 appear in feces already on the third day after infection, that is, much earlier than symptoms appear, which are sufficiently pronounced to send a person to the hospital and make him an official diagnosis (such symptoms may appear later two weeks), explained Tamar Kohn, a virologist at the Swiss Federal Institute of Technology in Lausanne. Monitoring the concentration of virus particles in wastewater will enable health officials to make informed decisions about measures such as isolation, she said. "A delay of seven to ten days can make a significant difference in the severity of this epidemic."
Earlier detection of coronavirus in a particular community will help limit the negative impact of COVID-19 on human health and the economy, especially if the virus returns next year, as Bibby explained.
Wastewater monitoring has been used for decades to measure the success of poliovirus vaccination campaigns, said Charles Gerba, a microbiologist at the University of Arizona at Tucson. This approach can be used to assess the effectiveness of measures such as social distancing, added Gerba, who found traces of SARS-CoV-2 in untreated wastewater in Tucson.
By Smriti Mallapaty