Israel has started analyzing wastewater for the novel coronavirus, SARS-CoV-2, to estimate the number of infections at a population level, according to Dr. Itay Bar-Or, head of the Health Ministry’s national lab for environmental virology. If successful, the method could also be used as an early-warning tool to alert the country to a second wave of infection.Sewage surveillance can account for those who are infected but have not been tested and are asymptomatic or have only mild symptoms, explained Bar-Or, who said that monitoring infection at this scale could provide better estimates for how widespread the virus is. “If you don’t have a lot of clinical tests, you can use environmental monitoring,” Bar-Or said. “You cannot get an exact number [of those sick], but you can get an approximation of the magnitude of infection.”Israel has been struggling to increase the number of people screened for COVID-19 since the virus arrived in the country in February. The Health Ministry said that it tested more than 12,000 people on Monday, but its goal since mid-March has been to screen 30,000 people per day.Bar-Or said that when he first learned of this new coronavirus, he raised the notion that the country could access a new layer of data with this sort of mass testing. He explained that if you identify the virus in wastewater that serves 100,000 people, and you know how to compute how the amount of virus shed in the feces can be modeled, you can then extrapolate the number of infected people in a population from these samples.Wastewater monitoring has been used in the country for decades to assess the success of its vaccination campaign against poliovirus. The unit was started in 1989.In 2013, the team discovered an outbreak of wild polio in the sewage, which Bar-Or explained is “not reproduced in sewage, only in humans, so we knew the virus was manifesting in the human population.”The Health Ministry then inoculated or gave polio vaccine boosters to the whole population of Israel and only a few children became infected. Bar-Or said the unit stopped what could have become a polio pandemic.“This is why the Health Ministry has made the decision for us to work on coronavirus,” he told The Jerusalem Post.Working with Prof. Ariel Kushmaro and Ehud Rinnot at Ben-Gurion University and Prof. Eran Friedler and Dr. Yair Lewis at Technion-Israel Institute of Technology, they first started testing stool on a small scale in the clinic. When initial tests showed the virus in the waste, they started collecting sewage.Bar-Or said that the country’s sewage consists not only of toilet water, but also shower, laundry machines and other wastewater. SARS-CoV-2 is shed by humans into this water. He said the virus “appears to be inactivated in wastewater,” meaning it appears that it cannot be transmitted through the sewage, as far as scientists now know – though Bar-Or stressed that this has not yet been verified.The team did multiple tests in the same location, tracking if the virus found in the sewage increased as the number of infected people did – and the numbers correlated.More worrisome, he said, would be if the numbers did not correlate, which is exactly how he hopes that the testing method will be used.“If you go to a city with only a small number of known sick people and you see a very strong signal in the sewage, you can say that something is wrong and more tests should be done,” he explained.Bar-Or noted that this method could be used to test sewage plants specific to senior living facilities, for example. If no trace of the virus is found, the country could assume residents are safe. If the virus is there, then residents and staff could be rapidly screened.In addition, the method would allow the country to make more informed decisions about which neighborhoods and cities to lock down – and when to lift their closures.“If you quarantine a region and then test the sewage in intervals – if you get a decrease of the virus in the sewage, you can say there is a decrease in sickness and you can use it as a parameter to take the closure off,” he said.Moreover, most researchers said they expect there will be a second wave of coronavirus next winter and screening the sewage through the national wastewater monitoring program could serve as an early-warning system. He said that just as was the case with polio, if the team starts to see a peak in the virus, we could start testing again. “We could preempt the illness,” Bar-Or predicted.Israel is not the only country examining this possibility. More than a dozen research teams worldwide are doing the same thing. There have been a handful of scientific extracts published by the United States, the Netherlands, Sweden and Australia.Israel has not been able to publish its results yet as they are still tweaking their methodology and “the team does not yet have 100% results,” though Bar-Or said that they do have the proof of concept.When could Israel expect to use this method as part of its arsenal against the coronavirus?“Within weeks it will be available,” he said.