By the end of 2020, the global COVID-19 death toll was emerging as cold weather in the Northern Hemisphere and holiday gatherings spurred immediate transmission of SARS-CoV-2 in the absence of a vaccine. Scientists and public health officials were desperate for new tactics to track the virus, which was moving faster than touch trackers, can simply remain active.
Tong Zhang, an environmental engineer and microbiologist at the University of Hong Kong (HKU), and his colleagues pioneered what was temporarily becoming a popular tracking method. They periodically collected sewage samples from about two dozen maintenance holes in the city and analyzed the sewage. For coronavirus DNA, with the Hong Kong government. In late December, they traced the outbreak to an apartment building where there were no symptoms of cases.
The government acted quickly. Authorities screened the building’s approximately 2,000 residents; nine tested positive. “These other people were isolated and went to a quarantine site. That’s how they stopped the chain of transmission,” Zhang said. After this success, he and his colleagues intensified their efforts.
Wastewater testing is still part of Hong Kong’s COVID-19 strategy today. Zhang’s team tests for the coronavirus at about 20 sites across the city each week, he says, and the team has expanded research on those samples to cover other pathogens. adding influenza, rotavirus, norovirus, and mpox, as well as markers of antimicrobial resistance. He sees wastewater testing as a way to assess the fitness of an entire community. “If we can make the method more standardized,” the tool becomes “a promising and exciting way” to detect pathogens around the world, adding those that scientists have yet to identify, he said.
Many scholars stick to these approaches. Lately there are more than 4,600 sites around the world where wastewater is collected for SARS-CoV-2 testing, and some of the study groups involved are investigating other potential applications, such as tracking illicit drug use and even cancer prevalence.
But it’s still up for debate whether this strategy has a chance of being effective in public fitness. Leo Poon, Zhang’s colleague at HKU’s School of Public Health, says more studies need to be done before fitness agencies expand their wastewater testing systems and incorporate this tracking of their regimen budgets. “There are still a lot of unknowns,” he says, especially in terms of testing for pathogens other than SARS-CoV-2. “I think there’s a steep learning curve right now: when we stumble upon something, what does it mean?
Many projects to track COVID-19 wastewater started the same way. Scientists learned early in the pandemic that SARS-CoV-2 could be detected simply in wastewater2 and contacted local water government and fitness agencies to download samples.
By the end of 2020, several studies had shown that coronavirus levels in public water systems could be correlated with the number of COVID-19 cases in the network. For example, researchers at Stanford University in California found that virus levels in wastewater rose and fell in other cases in the San Francisco Bay Area3. The organization that ran the paintings later discovered the WastewaterSCAN project, which analyzes samples from about two hundred sites across the United States (see “Transmission of Spikes”).
According to the scientists, in the most successful wastewater treatment projects, researchers collaborated directly with public health officials, who used the knowledge to design policies to protect against COVID-19. This has happened in rural Ghana, where, as in Hong Kong, wastewater testing has revealed cases of COVID-19 that had not been detected by other types of surveillance. Habib Yakubu, a public fitness researcher at Emory University’s Global Center for Drinking Water, Sanitation and Hygiene in Atlanta, Georgia, worked with a team of Ghanaians. The scientists expanded control strategies that take into account the country’s public sewers and limited laboratory equipment. They tried it in two rural districts, North Nanumba and Mion, where government officials suspected COVID-19 might simply spread, but clinical trials had not known any cases.
The researchers worked with network leaders to identify sampling sites, adding schools, gymnasiums, markets and waterways used for laundry. “We look at where other people converge,” Yakubu said. As a result, the government has stepped up public fitness activities, adding vaccination efforts and networked education. The team tested for other common diseases in Ghana, adding cholera and typhoid, which also influenced fitness actions.
For scientists at the Tata Institute of Genetics and Society in Bangalore, India, the need to monitor wastewater for COVID-19 became apparent after the devastating wave of the Delta variant of SARS-CoV-2 in the country in early 2021, Farah says. Ishtiaq, an evolutionary ecologist from Tata who runs the city’s COVID-19 surveillance program. She and her colleagues worked with the government to set up controls at 28 water treatment plants in Bangalore, a logistically challenging task, as the team had to collect samples manually rather than employing automated samplers, which is common in higher-income countries.
These tests proved a success when the Omicron variant spread in Bangalore the following year, Ishtiaq says. Knowledge of wastewater showed that Omicron variants were spreading widely in the city at a time when knowledge of fitness formulas was limited. Authorities have responded by renewing mask mandates and enforcing restrictions. in giant gatherings, he says.
Drawing inspiration from case studies like these, the box has grown particularly over the past four years, with many studies now conducting trials in 72 countries, according to the COVIDPoops19 panel put together by environmental engineer Colleen Naughton and colleagues at the University of California. see “Unequal Coverage”).
In December 2023 and January 2024, it became clear that COVID-19 spread widely in various parts of the world. But public fitness agencies have drastically scaled back their traditional testing and surveillance programs, leading to uncertainty about how widespread the coronavirus is spreading and a sudden focus on teawater-based epidemiology.
Some scientists and social media commentators have said that SARS-CoV-2 grades in wastewater are correlated with express case numbers, estimating massive increases in the U. S. But others have warned that wastewater surveillance is reliable enough to expect the actual number of infections. There’s a “false sense of accuracy” in such estimates, says Sam Scarpino, an epidemiologist at Northeastern University in Boston, Massachusetts, who has worked on COVID-19 knowledge systems.
Estimates are difficult to make because knowledge about wastewater differs particularly from traditional fitness indicators. In typical surveillance, knowledge constitutes individual inflamed Americans who can be identified by tactile tracing, isolated, and treated. In wastewater monitoring operations, knowledge can constitute entire communities.
According to them, “one liter represents a million people,” says Douglas Manuel, a fitness physician at the University of Ottawa in Canada. Manuel and his colleagues are aware of several variables that can adjust the effects of such tests; These come with population density, precipitation, pattern composition, handling and testing methods, and quality measures. 4 For example, when snow melts in the spring in Ottawa, it drains into the sewer formula and “washes away” counterfeit waste that might have accumulated in the pipes, Manuel says. This could interfere with the effects of SARS-CoV-2 measurements.
To account for those variables, researchers tend to compare a site’s measurements over time. The U. S. Centers for Disease Control and Prevention (CDC) has issued a statement of intent and prevention. The U. S. Department of Agriculture, for example, has developed a metric called the wastewater viral activity point that compares the recent rate of SARS-CoV-2 measurement to measurements beyond and then averages those comparison values across larger regions.
These comparative measurements can be useful in presenting the effects of wastewater to the public, although they make it difficult to perceive the complexity of the knowledge. Bilge Kocamemi, an environmental engineer at Marmara University in Istanbul and task coordinator for wastewater research in Turkey, says she temporarily learned that “The clinical representation of knowledge makes it unusable to the public. “Instead, she and her colleagues developed an undeniable map of COVID-19: Testing sites are displayed in other shades of yellow and green, depending on the highest degrees of SARS-CoV. This color scale is rarely very accurate, Kocamemi says, but it’s undeniable that it’s perceived by other people who don’t have clinical experience.
It’s difficult, but not impossible, to determine the number of cases (or other measures of the spread of COVID-19 in a community, such as the number of people who will be hospitalized) from levels of the virus in wastewater, say scientists analyzing this challenge. Such styles would make it less difficult for fitness officials to make policy decisions about wastewater data.
CDC’s Center for Epidemic Prediction and Analysis in Washington DC, created in 2022, is one of the teams tackling this challenge. Knowledge of wastewater is “a very smart indicator” of the burden of COVID-19 on hospitals, says Dylan George, the center’s director. In February, George and his colleagues launched new hospital prognostic models based, among other things, on knowledge of wastewater (see go. nature. com/43xumbz). Studies have shown that those models are maximally accurate when they use knowledge of wastewater in conjunction with knowledge of fitness formulas, which only one of those sources can provide. 5
George warns that more studies will be needed to better understand the link between virus levels in wastewater and disease levels in a community. For example, some scientists believe that virus levels could be updated as SARS-CoV-2 continues to mutate; a variant known as JN. 1 may simply cause other people to excrete more viral particles, or to excrete them for longer than previous variants, George says. “I think it will become an active field of study in the future. “
Modelers would like to have a more detailed understanding of clinical trials that would allow them to make greater comparisons between the effects of wastewater and network infections. The challenge is even greater for researchers testing wastewater for other viruses, says Casandra Philipson, a scientist at Ginkgo Bioworks, a Boston company. A company based on which it analyzes wastewater from airplanes and airports and conducts studies on new biosecurity tools. Philipson says you can have decent clinical knowledge about COVID-19, influenza, and syncytial virus respiration. But, he adds, “when you move away from those 3 pathogens, there’s actually a huge knowledge scarcity challenge. “
Some scientists are interested in a variety of other diseases and health signs that appear in human waste.
Bernd Manfred Gawlik, who coordinates the wastewater paintings at the European Commission’s Joint Research Centre in Brussels, calls them “the city’s dirty blood” and compares the wastewater samples to blood tests. “Now we’re starting to understand” how to diagnose this “blood” on a collective level, he says.
One of the usual targets of testing is antimicrobial resistance (AMR), an area of pre-pandemic wastewater studies. Ishtiaq, in Bangalore, says that “AMR is a huge challenge in this part of the world” because so many other people are on unregulated antibiotics. Their studies have expanded from COVID-19 testing to a multifaceted genomics platform capable of detecting viral and bacterial infections. Wastewater insights will help researchers understand which pathogens are CA infections and communicate that information to doctors, he says.
Fatma Guerfali, a molecular biologist and bioinformatician at the Pasteur Institute in Tunisia, is also tracking antimicrobial resistance in Tunisia, one of the countries considered most at risk. Guerfali says she and her colleagues are collaborating with the country’s fitness agency, as well as studio collaborators in other African countries, on how to maximize productivity to expand the program, which began with COVID-19 testing.
Beyond global goals such as antimicrobial resistance and influenza, priorities for wastewater testing differ depending on local fitness challenges. Because those tests can detect a wide variety of pathogens, scientists consult with fitness agencies to determine which goals to prioritize. In Ouisville, Kentucky, for example, Ted Smith, director of the Center for Air, Water and Soil Health at the University of Louisville, and his colleagues are testing a “panvirome panel” of about 30 pathogens of local interest to fitness. Last year, testing detected measles during an outbreak in the state, and fitness officials used the knowledge to inform vaccination programs, alerts to doctors and other fitness efforts, he says.
Another area of expansion is testing chemicals that humans excrete in wastewater. Some researchers, such as those at the Cambridge, Massachusetts-based startup Biobot Analytics, look for opioids and other drugs that pose a threat of misuse. Smith and his colleagues are testing wastewater for compounds indicative of exposure to air pollutants and have begun studies on lead levels. “Every day we find new things that we can question wastewater about,” he says.
Some researchers are even going beyond human-borne diseases to focus on animal-borne diseases. In 2022, scientists published paintings linking new SARS-CoV-2 variants discovered in New York City wastewater to the city’s rats6. Ishtiaq studies bird flu in Bangalore, and Ekta Patel, a scientist at the International Livestock Research Institute in Kenya, studies animal diseases there.
Patel and his colleagues are taking samples of slaughterhouse wastewater and 66 pathogens, adding anthrax, brucellosis and Rift Valley fever. To complement wastewater analyses, Patel hopes his team will be able to gather knowledge from veterinary clinics and hospitals in the network.
Some tea water scientists reflect on how different the early days of the COVID-19 pandemic might have been if a physically powerful global surveillance formula had been implemented for tea water. It’s possible that the researchers would have simply “immediately and retroactively analyzed tea water from all over the planet” as soon as the images of the virus were released, Scarpino says. This assessment may have led to a global list of places where SARS-CoV-2 is already spreading, informing methods to engage the virus even before clinical trials were widely available.
Scarpino argues that such a formula would require primary monetary investments, national and clinical leaders who can take charge of such projects, and criteria that would make wastewater knowledge more comparable across countries. 7
The existing COVID-19 testing network “was born out of necessity and chaos,” says Megan Diamond, who works on wastewater tracking at the Rockefeller Foundation in New York City. Global and regional establishments such as the World Health Organization, the European Union, and the Africa Centers for Disease Control and Prevention may want to step up their efforts and offer guidance on testing, knowledge sharing, and standards, Diamond says.
Gawlik has been participating in one such broad effort: the Global Consortium for Environmental and Wastewater Monitoring for Public Health, or GLOWACON, which was unveiled in Brussels in March. By recruiting more than 300 collaborators from around the world, including scientists, government officials and representatives of foreign organizations, in this consortium, it hopes to advance new strategies for diagnosing fitness disorders from the “mudblood” of cities around the world.
Nature 628, 492-494 (2024)
It’s me: https://doi. org/10. 1038/d41586-024-01092-7
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