Until the 1960s and 1970s, America’s inland and coastal waterways were literal dumping grounds for all manner of waste. From raw sewage in Boston Harbor to the burning Cuyahoga River, bodies of water were equal to dumpsters – a problem not isolated to the U.S. That was until laws like the Clean Water Act and decades of follow-up legislation stopped active pollution and found ways to clean the water around the nation and world. A by-product of this increased vigilance and enforcement of water quality resulted in greater study, domestically and internationally, of wastewater. But in recent months, it has increasingly become clear that robust and effectively managed wastewater systems may also serve as a valuable public health surveillance tool. Unobtrusive and relying on existing public health techniques, scientists are turning wastewater-based epidemiology into an early warning “tripwire” for viruses like COVID-19.
Since the COVID-19 virus began its spread around the globe last year, officials and health authorities have searched for ways of catching outbreaks before they surge and tax healthcare resources. In the spring of 2020, Massachusetts-based BioBot made international headlines for its discovery of COVID in Boston-area municipal wastewater. The study claimed to have clearly isolated COVID in wastewater at a regional Massachusetts treatment plant with samples collected in March. At the time, official COVID estimates for the region served by the wastewater treatment plant were under 500, but according to BioBot, the count of COVID infected was closer to 2,300.
Historical use of wastewater surveillance started in the mid-20th century but was not until the 21st century that its promise to a broader application to epidemiology was realized. Dealing with a polio outbreak in 2013, Israeli scientists traced the disease to a specific community after samples were automatically collected from wastewater trunk lines and analyzed for polio in fecal matter. In the same year, Swedish scientists examined wastewater for eight pathogens, hoping to create an early-warning system ahead of outbreaks, specifically for Hepatitis A and Norovirus, with the collected samples effectively identifying both illnesses before wide spread. When the cousin of COVID-19, SARS, appeared in China in 2003, the outbreak was tracked using wastewater surveillance. Today, scientists utilize similar methods to identify and track COVID-19, specifically by seeking out viral RNA in fecal matter.
Since the early April news, more time has been spent analyzing wastewater as a form of advanced warning or sentinel program in the fight against COVID. This month, the state of Utah announced the discovery of COVID in wastewater there, estimating 64% of 171 samples were positive for the novel virus. Dutch researchers reported in a pre-print that they came upon COVID in early March 2020, while municipalities in Texas and Florida have undertaken a similar analysis of wastewater, with the latter reporting “wastewater is chock-full of the virus.”
Published in the most recent Water Research, Spanish researchers found that COVID in wastewater from a specific region predicted a rise in cases among an otherwise unknown cohort. Researchers wrote their wastewater surveillance data, “were compared to declared COVID-19 cases at the municipality level, revealing that SARS-CoV-2 was circulating among the population even before the first cases were reported by local or national authorities in many of the cities where wastewaters have been sampled.”
A better view of the timeliness of wastewater-based epidemiology comes recently from Clemson, South Carolina, where the city and university have begun tracking COVID in waste streams with samples flagging cases before they appear among the public. Norman, professor at the University of South Carolina, said that with wastewater surveillance, “we’re able to test not only those people who are symptomatic … but we’re able to detect this in asymptomatic people who may not even know that they’re carrying it.” One of the continuing reasoning for social distancing and mask-wearing around the nation has been the potential spread of COVID in asymptomatic people.
Like in Massachusetts, the epidemiological surveillance provided by wastewater sampling has demonstrated the occurrence of COVID in cities earlier than expected. In the middle of June, Italian researchers reported that wastewater surveillance in Milan and Turin revealed the presence of COVID in those communities in December 2019. Utilizing samples taken between October 2019 and January 2020, researchers concluded the presence of the novel virus on the 18th of December, predating the first official case in the region by two months. Researchers in a pre-print report the presence of COVID in Parisian wastewater samples taken on March 5 before a spike in COVID-related deaths on March 10 with concentrations of COVID in wastewater precede clinical cases.
Spain, the United States, and France join country after country, including Japan, and India in the discovery of the predictive quality of wastewater surveillance in the age of COVID. Through regular, automatic sampling of wastewater will be vital in preventing renewed outbreaks of viruses like COVID. Adding viral RNA detection protocols to wastewater samples already regularly taken to detect contamination, illicit discharges or infiltration could be less logistically burdensome, and therefore potentially more cost-effective. The final potential social bonus is the noninvasive route of remote surveillance. And, where some communities distrust or are skeptical of broad or random testing for religious or civil liberties reasons, the use of wastewater-based epidemiology surveillance removes concerns over privacy invasion or the forfeiture of personal integrity rights.
Image courtesy of Flickr. Originally published by S&S on July 8, 2020.
