A place to observe human health in real time.
Wen 丨 He Qianming
Edited by 丨 Huang Junjie
The COVID-19 pandemic has made people accustomed to a lot of otherwise less common biotechnologies, such as inserting a sampling stick about 10 centimeters long into the nostrils or stirring the throat for nucleic acid testing, becoming the first line of defense against the new crown epidemic.
Another testing method is becoming more widespread as the outbreak spreads: catching traces of the new coronavirus through sewers.
Since January 2022, in the face of the rapidly spreading Olmikron strain, many countries in Western Europe, as well as the United States, Canada, Japan, Singapore and other places, have begun to relax their epidemic prevention policies and gradually stop large-scale nucleic acid screening. But easing is not the same as ignoring it, and sewer wastewater testing has become a common COVID-19 tracking tool in these areas.
According to data compiled by researchers at the University of California, Merced, 66 countries have now officially enabled or studied monitoring the COVID-19 epidemic through sewers, 12 more than a year ago.
Before the new crown
An important application for monitoring wastewater is anti-narcotics
Polio (polio) could become the next epidemic virus to be eliminated by vaccines – a rare full-scale victory for humans.
The disease was once a nightmare for young parents in big cities, where the virus was excreted through feces and then entered the human body through contaminated water sources or other means, causing infection, paralyzing or even dying in severe cases. The 1916 pandemic in New York city killed more than 2,000 people.
Vaccines developed in the 1950s suppressed the virus. However, the poliovirus still appears sporadically, it has a long incubation period of more than 1 month, and 90% to 95% of infected people are asymptomatic – and can also be transmitted if asymptomatic.
The means of testing is sewer detection, a very manual method: open the sewer manhole cover, scoop out the wastewater mixed with human feces, pour it into glassware, send it to pasteurization, and then precipitate, filter, concentrate, purify, and then detect the virus. If tested regularly, the prevalence of the virus can also be estimated.
It is thanks to the wastewater system that Israel detected traces of the virus earlier in 2013, buying time for vaccination, carrying a wave of polio outbreaks, and finally no one was paralyzed.
After poliovirus became rare, wastewater monitoring was commonly used in countries to analyze illicit drug or drug use in a region.
In 2005, italian researchers measured cocaine residues in the Po River and found nearly 10 pounds per day, and they estimated that residents living in the Po River Valley smoked 40,000 doses of cocaine per day, nearly three times the official monthly consumption.
Because of the effective analysis of drug and illicit drug levels, wastewater testing is making its way into more countries. In 2010, a consortium of European researchers formed a unified analysis of the drug situation in European wastewater and submitted the results to the European Office on Drugs and Crime.
In 2018, the nature magazine website reported on the construction of a wastewater poison testing system by Li Xiqing, a professor at Peking University, and Zhongshan City, Guangdong Province. According to the Southern Network, people involved in the development of the system said that mixing 5 grams of drugs into the water of the West Lake can also be detected, and it is also possible to estimate how many drug users and which types of drugs are mainly smoked based on wastewater. In September 2020, the Narcotics Control Bureau of the Ministry of Public Security of China required that the anti-narcotics corps of each province test wastewater quarterly starting in 2021.
The coronavirus continues to circulate
Wastewater monitoring systems are constantly being improved
People infected with the new crown virus, even if they do not have symptoms, will have the new crown virus in their feces. Detecting wastewater in sewers is equivalent to doing a nucleic acid test for everyone in an area together, the principle is the same as a nasal swab, except that the sample is feces, but the accuracy is also guaranteed.
When the COVID-19 pandemic first broke out globally, researchers in some European countries and the United States began analyzing wastewater in sewers to track the covid-19 epidemic. Chinese mainland, some scholars have done research, such as the Wuhan Institute of Virology of the Chinese Academy of Sciences, which has analyzed the wastewater near the designated hospital of new crown pneumonia in Wuhan.
Many researchers have found that when the number of COVID-19 infections in a region increases, the amount of COVID-19 in quantitatively tested wastewater also increases. Because people infected with the new coronavirus will excrete the virus days or even a week before they develop symptoms, wastewater testing may also be an early warning.
On August 25, 2020, logistics staff at the University of Arizona in the United States regularly tested for wastewater in student dormitories and tested positive for nucleic acid. The school immediately checked 311 students and staff within the scope of wastewater discharge, found 2 asymptomatic infected people, and a cluster of outbreaks was eliminated ahead of schedule.
Chart: Before the rise in the number of confirmed cases, the U.S. city of Minneapolis had detected changes in the concentration of the new coronavirus in wastewater
However, the wastewater monitoring system originally established for drugs and polio viruses is not enough to help people better prevent and control the new crown virus. Previous applications did not require high-frequency detection, often only quarterly, monthly detection, and European and American countries from the sewer sampling or manual, can not keep up with the speed of Omikeron.
The accuracy of the new crown virus in wastewater testing is also vulnerable to environmental influences. For example, if it rains in the sampling area, the concentration of the new crown virus in the sewer will drop, and the results will change.
With the COVID-19 epidemic, wastewater monitoring has been paid more and more attention, and these problems have gradually been solved. Startups are now joining in, trying to use IoT devices to automatically collect wastewater in sewers and send it to the lab for analysis, reducing manual intervention.
Researchers have also found ways to make wastewater analysis more accurate. According to the journal Science, researchers have tried to calibrate the test results of the new crown virus with a virus commonly found in wastewater. One candidate is the capsicum mild mottled virus (PMMoV), which is widely distributed and remains stable 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 does not know exactly who the virus is coming from. If you want to actively prevent the epidemic with this data, you must isolate and test one by one after monitoring the signs of outbreak.
The coronavirus may persist in the intestines for a long time, which also causes problems for wastewater monitoring.
A Stanford team published a paper in April in which they followed 113 cases of COVID-19 infections with mild to moderate illness. These people have recovered 10 months after infection, and the nasal swab nucleic acid test has turned negative, but 4% of them still have the new crown virus detected in their feces.
Jin Dongyan, a professor and virologist at the University of Hong Kong, told LatePost that if their feces are tested for nucleic acid, the results may be positive, even if these infected people have recovered, the new crown virus in the body is not contagious.
In his view, the most effective time for wastewater testing for the new crown virus is when a virus appears in an area from scratch or when the virus spreads early. At a time when the coronavirus is widespread, data on monitoring wastewater may be helpful in predicting the development of the virus, but the effectiveness will be reduced.
It may become an integral part of the field of public health
As some countries and regions relax COVID-19-related controls, wastewater testing has become a means of regularly tracking COVID-19. In February, several U.S. states canceled indoor mask orders, and the U.S. Centers for Disease Control and Prevention (CDC) began regularly updating wastewater testing data on its official website, believing that it could provide early warning for the spread of the new coronavirus at the community level.
Just as the COVID-19 pandemic has made mRNA technology a new way to make vaccines, the COVID-19 pandemic has demonstrated the potential power of wastewater surveillance.
Many researchers believe that a well-developed wastewater monitoring system could help prevent the next pandemic. Researchers in Italy retrospectively found in 2021 that in December 2019, when covid-19 patients were diagnosed in Wuhan, the same virus was already in the sewers of Milan.
There is also a hidden mutation of the new crown virus in the wastewater. For example, a few days before South Africa reported the new coronavirus Olmiqueron (later named) strain on November 25, 2021, it was detected in the sewers of New York. No one realized at the time that the strain would unleash an unprecedented wave of infections in a few months' time.
From nucleic acid testing, which was used at the beginning of the outbreak in 2020, to today's supplementary antigen testing and wastewater testing, people's means of tracking the new crown epidemic are escalating.
An EU environment commissioner said wastewater monitoring provides a more cost-effective, fast and reliable source of information for tracking the coronavirus epidemic. Last March, the European Union required member states to test wastewater to track the coronavirus and its variants, and this year 1,370 wastewater treatment plants have been regularly tested. They also intend to propose legislation to establish a permanently operational wastewater surveillance epidemiology system.