One of the big challenges in addressing the spread of the coronavirus, and in lifting social-distancing restrictions, is identifying hot spots of illness and infection. Without this, any attempt to exit the crisis could set off an uncontrollable outbreak.
Researchers around the world, including in Israel, are looking for ways to monitor wastewater for traces of the virus that COVID-19 patients are known to excrete in urine and feces.
The structure of sewage systems allows for the monitoring of effluent from a specific area, says Eran Friedler, a professor in the civil and environmental engineering department of Israel’s Technion technology institute. He is part of an Israeli effort to develop a monitoring system that could determine the infection rate in a neighborhood, for example.
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“Such a system will make it possible to test entire populations and compare the strength of various signals in the presence of the virus and focus on high-infection areas,” Friedler says.
The hope is to identify hot spots at an early stage and target these areas for testing and, if needed, for restrictions. Studies have shown that COVID-19 patients begin shedding the virus in feces before they show any symptoms and even if they never develop symptoms.
More than a dozen research groups around the world are trying to develop sewage monitoring methods for the virus. Scientists in the Netherlands, the United States and Sweden have identified the virus in wastewater.
Among the challenges are concentrating the samples sufficiently to detect the virus and measuring its presence accurately, as well as determining where to gather samples in order to obtain the most accurate picture of the spread of the virus.
There are still a number of unknowns, including the amount of virus shed by the average COVID-19 patient in feces, which is critical for extrapolating the number of people with the illness from the concentration of the virus in wastewater.
A study carried out in Massachusetts and published this week on a public server prior to formal peer review found traces of the coronavirus at a sewage treatment facility served by an unidentified “large metropolitan area” in the state. The researchers said their analysis suggested that there were between 2,300 and more than 115,000 people infected with the virus, in an area with just 446 confirmed cases of COVID-19.
Researchers in the Netherlands reported in an earlier article that they had detected the virus in a particular community before even a single person there was diagnosed with the disease.
Wastewater monitoring has been used to detect the presence of the viruses that cause polio and measles, outbreaks of norovirus, which causes gastroenteritis, and the presence of antibiotic-resistant bacteria, among other materials. In Europe the method is also used to estimate the extent of drug abuse in various populations.
For years, the Health Ministry has monitored wastewater to detect polio outbreaks. In 2013, it detected an outbreak in southern Israel that prompted a vaccination campaign that stopped the disease’s spread.
The Israeli teams includes, in addition to Friedler, Prof. Ariel Kushmaro, the head of environmental biotechnology at Ben-Gurion University of the Negev; Dr. Yair Lewis of the Technion; and Dr. Itay Bar-Or, the head of the national center for environmental virology at the Health Ministry.