Itf the past two years have taught us anything, it’s that testing for viral diseases is complicated. Some tests can be difficult to obtain, as was the case with COVID-19 in its early years. Even if they have the ability to test, it is possible that they don’t feel they are required. People with COVID-19 often don’t have symptoms and may not always know to get tested. And now, with the availability of at-home self-tests, most people test themselves and don’t report the results. With other diseases—such as monkeypox—stigma surrounding the disease and the group most affected can deter access to testing.
These limitations hinder health authorities’ ability to learn more about infectious diseases and control their spread. If you can’t detect a problem, you can’t direct resources to help fix it.
Some of these problems can be avoided by analyzing wastewater. Scientists have tracked COVID-19 through wastewater since early in the pandemic, and now they’re doing the same for monkeypox. Researchers at Emory University and Stanford University have launched a new program to monitor monkeypox cases. They analyze sewage samples from 41 cities in 10 states. The monkeypoxvirus has been detected in 22 of these sites. This information proves valuable for patients and doctors as they struggle with the testing process. “We have now detected monkeypox DNA in sewersheds before any cases were reported in those counties,” says Bradley White, senior staff scientist at Verily. They plan to soon publish the first results of their monkeypox research in a paper. While other academic- and public-health organizations are also working with local sewage plants to monitor the virus, this WastewaterSCAN program is focused on obtaining a nationwide picture of cases.
These data were shared on a Stanford website. The group will also share its findings with U.S. Centers for Disease Control and Prevention.
Continue reading: How the Monkeypox Virus Does—and Doesn’t—Spread
The sewage, which is made up of thousands of individuals, provides an excellent, anonyme way to determine the level of virus within communities. “We are capturing cases even if people are asymptomatic,” says Marlene Wolfe, professor of environmental health at Emory and co-principal investigator of WastewaterSCAN. “When there is limited testing capacity, and there is stigma associated with the disease, to have a population-level measurement of infections that isn’t impacted by those things is really powerful.”
One reason sewage can be used to detect monkeypox is because it has effluent that comes from both urine and stool. The virus can also be expelled from saliva. Since monkeypox is active in skin lesion, these secretions make it a powerful tool for detecting and trapping the virus.
Since the 1930s, wastewater has been studied by researchers. The most notable example was during the war years to monitor polio outbreaks in America. The COVID-19 epidemic proved their utility. Research has shown that samples of waste can detect signs of SARS CoV-2 within a week. This is before the clinics start receiving positive cases. Wastewater can even detect new variants of SARS-CoV-2—something a rapid test can’t do.
In late 2020, the CDC launched the National Wastewater Surveillance System (NWSS), the first federal system to track an infectious disease pathogen—in this case, SARS-CoV-2—in sewage. It’s an attempt to standardize the way wastewater is collected, analyzed, and interpreted. NWSS now includes data from local programs—like WastewaterSCAN—and cities with their own tracking systems. New York City’s Biosurveillance Program, for example, has been testing wastewater for signs of SARS-CoV-2 since February, and now 11 hospitals in the group will start scanning for monkeypox and polio, which have been detected in New York City sewage.
When monkeypox cases first began popping up in the U.S., the researchers at Stanford, Emory, and Verily saw an opportunity to apply a wastewater lens to the disease, especially since testing for monkeypox wasn’t widely available. Since November 2020 they had been monitoring SARS-CoV-2 in a handful of California sites through the Sewer Coronavirus Alert Network. They also had begun adding analysis for other viruses such as influenza and RSV. Monkeypox was spreading all over the globe and although testing resources were limited at the time, the team added the virus to their investigation and expanded the network to cover more locations. WastewaterSCAN is now a reality.
Wolfe says the group’s platform for isolating the genetic material of microbes made it relatively easy to create the proper assay for detecting the monkeypox virus in mid-June. Their probe identified the virus using a unique portion of the monkeypox DNA. But, says White, “the first few tests we ran on wastewater samples didn’t pick anything up.” That might have been because the concentration of virus in sewage at that point was so low. While WastewaterSCAN’s probe is designed to pick up very diluted amounts of virus, at the time of the tests, there were few cases in northern California. WastewaterSCAN began sampling daily water from San Francisco treatment plants on June 19th. Both sites were positive for monkeypox the next day.
Continue reading: Monkeypox. What is it really like?
The monkeypox virus’ genetic material differs from that of SARS-CoV-2 because it’s in the form of DNA, while the COVID-19 virus and all of the group’s previous tests had been directed against RNA. But, White says, “DNA is much more stable than RNA, so as long as the genetic material is extracted from the sample, we’re pretty confident that if people are excreting a virus in wastewater, we will eventually detect it.”
According to scientists, there remain a number of important questions regarding monkeypox and wastewater. They don’t have enough data to say for sure how much of a lead time wastewater can give health officials about rising cases, compared to testing at clinics and hospitals. To get an accurate picture of what level of virus is needed in a community or the number of cases that must accumulate in one region to detect signs of the disease in sewage, they are continuing to analyse the data. Doctors could use this information to prepare sufficient numbers of vaccines and treatment options for the disease, so they can get ahead of cases.
The WastewaterSCAN team is now applying what they’ve learned from COVID-19 and monkeypox to explore ways to monitor influenza, RSV, and other seasonal diseases. RSV, which is a serious respiratory illness that can infect babies and causes severe symptoms, could be prevented by doctors being able to identify the areas where they are spreading.
Wolfe states that coordination between partners is key to creating such a national system. “Having a network of sites that use the same collection and analytic methods so we can compare data gives us a national picture of what is going on,” she says. “We’d love to have more federal investments in systems like this.”
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