Look for the corona virus in the sewers

In the Netherlands and other countries they have already begun to look for the presence of corona in municipal waste water. This step can apparently save a lot of individual tests and promote a more effective fight against the virus. Will the model be adopted in Israel soon?

By Zwata - Science and Environment News Agency

One of the most frustrating aspects of the corona crisis is the uncertainty surrounding it. Thus, for example, there is a real difficulty in estimating the extent of the morbidity of the disease (COVID-19) caused by the new corona virus (SARS-CoV-2): in order to estimate the number of patients in a certain area and especially the asymptomatic patients (in whom the symptoms of the disease do not manifest), It is necessary to perform a very large number of tests, the availability of which is limited. A new method, which has already yielded results in different parts of the world, makes it possible to map the levels of the corona disease in a certain area and to predict future outbreak centers efficiently, this through the sewers.

Similar to various substances in our body, the corona viruses are also released in the feces of a person who is infected with them, so by examining the wastewater of a neighborhood or settlement, it is possible to learn about the state of corona morbidity in that place. In some cases, the envelope of the virus breaks down in the wastewater, so sometimes only parts of it can be found, but even in this situation, the RNA of the virus - its hereditary material - can still be identified. "In this test, we examine whether the RNA sequences found in the sewage match those of the virus, and according to the results, determine whether there is SARS-CoV-2 in the place and quantify its presence," says Prof. Dror Avisher, head of the Center for Water Research at Tel Aviv University.

According to the evidence that exists today, the corona virus ceases to be active when it reaches wastewater, and therefore there is apparently no danger of it spreading and infecting humans at this stage of its existence - nor when the wastewater undergoes purification at the Wastewater Treatment Institute (WTP) and is used to irrigate agricultural crops .

Corona at the airport

Today, over a dozen research groups are conducting tests in wastewater in various parts of the world in search of information that will lead to a better understanding of the corona morbidity in those areas. So far, thanks to the method, traces of the virus have been found in the Netherlands, the United States and Sweden. Researchers have revealed the presence of remains of corona viruses At the Schiphol Airport in Amsterdam only four days after the first case of the virus was discovered in the entire Netherlands, and RNA of the virus was detected in the Dutch city of Amersfoort even before the discovery of the first patient there.

The use of the method is still in relatively early stages. There is still a need to fully understand the amount of virus that is released from a single person in the feces, in order to be able to properly conclude how many infected people represent the concentrations found in the sewage. In addition, the scientists must find out what the sensitivity threshold of the tests is - that is, below what concentration the virus will not be detected in the test even if it is present in the sewage.

Either way, there is no doubt that such a test has many advantages. The first of these is the early detection: as we know, the symptoms of the corona may appear up to 14 days after infection, a time during which the person does not know that he is infected with the virus and may spread it to many people in his environment. In the feces, on the other hand, the virus already appears Three days after infection, which makes it possible to carry out faster actions to isolate the center of infection, which can significantly reduce the spread of the disease in the area (such as imposing a targeted closure or curfew).

In some cases, examining the presence of the corona virus in sewage may provide information about the spread of the disease in a specific area more effectively than the individual corona tests. "With this method, it is possible to obtain information on very broad scales using relatively few tests," says Dr. Eddie Citrin, an environmental microbiologist at the Volcanic Institute. "If you want to see what the spread of the virus is in Bnei Brak, for example, and check there person-by-person, it is necessary to conduct several tens of thousands or hundreds of thousands of tests. On the other hand, if you simply check the sewage in the neighborhoods in Bnei Brak, you can relatively easily monitor the level of the corona and see which neighborhoods are affected, and get a very broad picture," he says.

However, this method also has limitations. One of them lies in the fact that the information it provides is very general. "This method is very good at the macro level, but not at the micro level," says Citrin. "Even if we find out thanks to her that there is a lot of sickness in a certain neighborhood in Jerusalem, for example, we won't be able to know who the sick people are. In the end, the personal and general tests should come together."

Another limitation of the test lies in the environment in which it is carried out: the sewage, which by its nature is far from sterile. "The sewage is very mixed with other things: besides the toilet water, it also gets waste from all the sinks, washing machines, showers and more," says Citrin. This sewage contains various cleaning agents that may reduce the concentration of the virus in the sewage and prevent it from being detected.

Wastewater for routine

Detecting remains of viruses in waste water is not a new patent, and even long before the Corona days it was used around the world for the purpose of monitoring various diseases that leave evidence in feces and urine. Over the years the method has been used also in Israel: In 2013, a test he conducted The National Center for Environmental Viruses In the sewers, Berhat revealed the existence of the polio virus in Israel (without any patients with the disease being discovered), and later it was also discovered that the virus was spreading to the center of the country, which led to an extensive vaccination campaign in which a vaccine was given that contained weakened polio viruses (as opposed to the vaccine that is routinely given that contains a killed virus). With the administration of the attenuated virus vaccine, a decrease in the polio virus population was observed in the sewage systems in Israel, and by April 2014, its presence was no longer found in the sewage. In 2016, the presence of the hepatitis A virus was observed in the sewage water in Israel, which helped in locating the source of its outbreak, which was in the Tel Aviv area.

According to Citrin, it is important to carry out tests for the new corona virus in wastewater in Israel as well, alongside the personal tests, and this could help the decision makers in the country in planning a strategy for the gradual return to normalcy in the shadow of the corona. "Maybe the sewage can give us a good indication of how many carriers there are everywhere," he concludes. "We need to start thinking about how to get out of the crisis in a gradual and balanced way and how to return to some sort of semi-normal routine, and we need to rely in this process on data and very in-depth knowledge on the subject."

The Ministry of Health responded: "We are familiar with the publications from the Netherlands and the world regarding the presence of the corona virus in wastewater. This is a research activity at this stage. The Ministry of Health's laboratory for environmental viruses, researchers from Ben Gurion University, and from the Technion are currently conducting tests in wastewater to detect the corona virus. The tests are done at wastewater treatment facilities and at other points in the pipelines transporting the wastewater to the treatment facilities. After analyzing the results of the samples, we will be able to assess whether sewage sampling can be used for the early detection of an outbreak of the corona virus and under what conditions."