EDMONTON -- As more countries turn to wastewater testing to measure the spread of COVID-19, researchers say more studies need to be done to ensure that wastewater containing coronaviruses do not pose a risk to human health.
A global study led by researchers from the Zuckerberg Institute for Water Research at Ben-Gurion University of the Negev (BGU) evaluated recent studies on coronaviruses and other airborne infectious diseases, including SARS and MERS, in wastewater to weigh the threat to human health.
Though researchers were unable to answer the question of whether wastewater containing these diseases could be infectious, they warn that sewage leaking into natural watercourses could lead to infection via airborne spray, prompting calls for more research.
“There is ample reason to be concerned about how long coronaviruses survive in wastewater and how it impacts natural water sources," lead author Dr. Edo Bar-Zeev of the BGU Zuckerberg Institute said in a press release.
“Can wastewater contain enough coronaviruses to infect people? The simple truth is that we do not know enough and that needs to be rectified as soon as possible.”
The study notes that it remains unclear whether treated wastewater used to fill lakes and rivers could become sources of contagion, or whether produce irrigated with wastewater and not properly disinfected could be an indirect infection route.
"Wastewater treatment plants need to upgrade their treatment protocols and in the near future also advance toward tertiary treatment through micro- and ultra-filtration membranes, which successfully remove viruses," Bar-Zeev and his colleagues say.
Yet, despite researchers like Bar-Zeev sounding the alarm on the potential risks of wastewater, the World Health Organization (WHO) says that to date no infectious SARS-CoV2 virus has been recovered from untreated or treated sewage.
“Given the myriad pathogens routinely expected to be found in untreated sewage and the commensurate precautions normally taken, sewage sampling in the context of COVID-19 is not expected to engender any additional infection risk to workers,” said the WHO in an Aug. 9 briefing.
A growing number of countries have turned to wastewater testing to track community outbreaks of COVID-19, including Italy, Australia, the Netherlands, and the U.S.
In fact, traces of SARS-CoV-2, the virus that causes COVID-19, were found in samples of waste water collected in Milan and Turin, Italy, at the end of last year -- more than two months before the country's first case was officially detected.
Canadian researchers have also been using wastewater to track the spread of the novel coronavirus in several provinces in the hopes of expanding testing to rural areas that may not have rigorous testing capabilities.
“People who have COVID-19, whether they have symptoms or not, excrete particles of the virus which go into the wastewater treatment plant. So, you can sample the wastewater treatment plant to see if there are particles there,” Gail Krantzenberg, a McMaster University professor leading one of these studies, told CTV News Channel in July.
“We can also track where in the communities there might be spikes, by going into the sewage system and canvasing for the virus in the sewage system on the way to the wastewater treatment plant.”
Most countries are using wastewater in the context of research studies. However, the Netherlands plans to incorporate daily sewage surveillance into its national COVID-19 monitoring system.
