The new crown epidemic has made people accustomed to many biotechnologies that were not so common before, such as inserting a sampling stick about 10 cm long into the nostril or throat for a few turns for nucleic acid testing, which has become people’s first line of defense against the new crown epidemic.
Another detection method is gaining popularity as the epidemic spreads: catching traces of the new coronavirus through sewers.
Since January 2022, many countries in Western Europe, as well as the United States, Canada, Japan, Singapore and other places have begun to relax epidemic prevention policies and gradually stopped large-scale nucleic acid screening in the face of the fast-spreading Omicron strain. But relaxing does not mean disregarding, sewer wastewater testing has become a common method of tracking the new crown epidemic in these areas.
According to data compiled by researchers at the University of California, Merced, 66 countries have officially implemented or studied the monitoring of the new crown virus epidemic through the sewers, 12 more than a year ago.
before the corona
An important application of monitoring wastewater is drug detection
Polio (polio) could be the next pandemic virus to be wiped out by vaccines—a rare all-out victory for humans over viruses.
This disease used to be a nightmare for young parents in big cities. The virus is excreted from the body through feces, and then enters the human body through polluted water sources or other means to cause infection, and severe cases can be paralyzed or even killed. The 1916 New York City pandemic alone killed more than 2,000 people.
Vaccines developed in the 1950s suppressed the virus. But the polio virus still emerges sporadically, it has a long incubation period that can exceed a month, and 90% to 95% of infected people are asymptomatic—and contagious when they are asymptomatic.
The detection method is sewer detection, which is very manual: open the manhole cover, scoop out the waste water mixed with human feces, pour it into glassware, send it to pasteurization, then precipitate, filter, concentrate, purify, and then Detect viruses. If tested regularly, it can also estimate the prevalence of the virus.
It is by relying on the wastewater system that Israel discovered traces of the virus earlier in 2013, buying time for vaccination, and enduring a wave of polio epidemics, and no one was paralyzed in the end.
After the polio virus became rare, countries often used wastewater monitoring to analyze the use of illicit drugs or drugs in a region.
In 2005, Italian researchers measured cocaine residues in the Po River and found nearly 10 pounds a day. Based on this, they estimated that residents living in the Po Valley were smoking 40,000 doses of cocaine a day, which is the official monthly consumption. nearly 3 times.
Wastewater testing is entering more countries because of its ability to effectively analyze drug and illicit drug content. In 2010, a consortium of European researchers formed a unified analysis of drugs in European wastewater and submitted the results to the European Office on Drugs and Crime.
In 2018, the website of “Nature” magazine reported on the wastewater poison inspection system built by Professor Li Xiqing of Peking University and Zhongshan City, Guangdong Province. According to Nanfang.com, the people involved in developing the system said that 5 grams of the drug can be detected by mixing as much water as the West Lake, and it can also estimate how many drug addicts there are and which types of drugs they mainly consume based on the wastewater. In September 2020, the Narcotics Control Bureau of the Ministry of Public Security of China required that from 2021, the anti-drug corps of each province will test wastewater quarterly.
The novel coronavirus continues to spread
Continuous Improvement of Wastewater Monitoring System
People infected with the new coronavirus, even if they do not have symptoms, will have the new coronavirus in their feces. Detecting wastewater in the sewer is equivalent to performing a nucleic acid test on everyone in a certain area. The principle is the same as that of a nasal swab, except that the sample is feces, but the accuracy is also guaranteed.
When the new crown epidemic first broke out in the world, researchers in some European countries and the United States began to analyze wastewater in sewers and track the epidemic situation of the new crown virus. Scholars in mainland China have also done research. For example, the Wuhan Institute of Virology of the Chinese Academy of Sciences has analyzed the wastewater near the designated hospital for new coronary pneumonia in Wuhan.
Many researchers have found that when the number of new crown infections in an area increases, the amount of new coronavirus in the wastewater that is quantitatively detected will also increase. Because people infected with the new coronavirus shed the virus days or even a week before symptoms appear, wastewater testing also has the potential to provide early warning.
On August 25, 2020, when the logistics staff of the University of Arizona in the United States regularly tested the wastewater of the student dormitory, the nucleic acid showed positive. The school immediately checked 311 students and staff within the wastewater discharge area and found 2 asymptomatic infections, and a clustered outbreak was eliminated ahead of schedule.
Figure: Before the number of confirmed cases rose, the city of Minneapolis in the United States had detected changes in the concentration of the new coronavirus in wastewater
However, the wastewater monitoring system originally established for drugs and polio virus is not enough to help people better prevent and control the new crown virus. Previous applications did not require high-frequency inspections, and were often only inspected every quarter or month, while European and American countries still sampled from sewers manually, which could not keep up with the speed of Omicron.
The accuracy of wastewater detection for Covid-19 is also susceptible to environmental impacts. For example, if it rains in the sampling area, the concentration of the new coronavirus in the sewers will drop, and the results will change.
With the new crown epidemic, more and more attention has been paid to wastewater monitoring, and these problems have been gradually solved. Now there are startups joining in, trying to use IoT devices to automatically collect wastewater in the sewer, and then send it to the laboratory for processing and analysis, reducing manual intervention.
Researchers have also found ways to make wastewater analysis more accurate. According to the “Science” magazine, some researchers have tried to calibrate the test results of the new coronavirus with viruses commonly found in wastewater. One candidate is pepper mild mottle virus (PMMoV), which is widely distributed and has stable concentrations in human feces throughout the year. If the wastewater is diluted by rainwater, researchers can determine how prevalent the new coronavirus is based on changes in PMMoV concentrations.
The technically intractable problem is that wastewater testing cannot tell precisely which person the virus came from. If we want to use this data to actively prevent epidemics, we must conduct targeted isolation and one-by-one testing after monitoring signs of outbreaks.
The new coronavirus may persist in the gut, which also poses problems for wastewater monitoring.
A Stanford University team published a paper in April in which they followed 113 COVID-19 patients with mild to moderate symptoms. After 10 months of infection, these people have recovered, and the nucleic acid test of nasal swabs has turned negative, but 4% of them still have the new coronavirus detected in their feces.
Jin Dongyan, a professor and virologist at the University of Hong Kong, told LatePost that if a nucleic acid test is performed on their feces, the result may be positive, even if these infected people have recovered and the new coronavirus in their bodies is not contagious.
In his view, the most effective time for wastewater to detect the new coronavirus is when the virus has emerged from scratch or early spread of the virus in an area. At a time when the new coronavirus is widespread, monitoring wastewater data may be helpful in predicting the development of the virus, but its effectiveness will be compromised.
may become an integral part of public health
Wastewater testing has become a regular means of tracking Covid-19 as some countries and regions relax controls related to Covid-19. In February of this year, many states in the United States lifted indoor mask orders, and the Centers for Disease Control and Prevention (CDC) began to regularly update wastewater testing data on its official website, believing that it could provide early warning of community-level spread of the new coronavirus.
Just as the COVID-19 pandemic made mRNA technology a new way of making vaccines, the COVID-19 pandemic has also demonstrated the potential power of wastewater monitoring.
Many researchers believe that a comprehensive wastewater surveillance system can help prevent the next pandemic. Italian researchers backtracked in 2021 and found that in December 2019, when a patient with new coronary pneumonia was diagnosed in Wuhan, the same virus was already present in Milan’s sewers.
There is also a mutation of the new coronavirus hidden in the wastewater. For example, South Africa reported the Omicron (later named) strain of the new coronavirus on November 25, 2021, which was detected in New York’s sewers. No one realized at the time that this strain would set off an unprecedented wave of infections a few months later.
From the nucleic acid test, which was adopted at the beginning of the outbreak in 2020, to the increasing popularity of supplementary antigen test and wastewater test today, people’s means of tracking the epidemic of the new crown are being upgraded.
Wastewater monitoring provides a more cost-effective, fast and reliable source of information for tracking the coronavirus epidemic, an EU environment commissioner said. In March last year, the European Union asked member states to test wastewater to track the new coronavirus and its variants, and 1,370 wastewater treatment plants have been regularly tested this year. They also intend to propose legislative proposals to establish a permanently operational wastewater surveillance epidemiological system.
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