Representative image. Photo: Glavo/pixabay.
In countless Hollywood films, the good guys have chased villains into sewers, splashing muck over themselves before crawling victorious out of manholes. Similarly, in the time of COVID-19, many researchers around the world have been chasing the novel coronavirus in sewers.
The term that describes this adventure – wastewater-based epidemiology (WBE) – has been in use for several decades, to surveil diseases and drugs in the natural environment. Studies from past epidemics caused by coronaviruses have shown that viruses are excreted in infected people’s faeces, and as such have been detected in sewage as well. So mapping where they are found can help determine if there could be infections of the virus in a given area.
Traces of the novel coronavirus have also been detected in sewage, according to studies from at least 10 countries, although researchers’ efforts have been concentrated in a few developed countries. These efforts have typically been led by a government department in charge of regulating water use.
For example, the Syndicat Interdépartemental pour l’Assainissement de l’Agglomération Parisienne (SIAAP) in Paris started began testing sewage for the novel coronavirus even when the number of reported cases in the city were low, and detected high concentrations. This result indicated that the city already had a large number of asymptomatic people, Sam Azimi, who works at SIAAP, said at a webinar. The body has since set up an ‘epidemiologic observatory’ to share information between scientists and wastewater utilities in France.
Christoph Ort, of the Swiss Federal Institute of Aquatic Science and Technology (EAWAG), said the virus’s load in sewage is probably linked to the number of COVID-19 patients in an area. Research indicates WBE can detect a person with COVID-19 in a population range of 100 to 2 million.
KWR Water Research Institute in The Netherlands detected fragments of the virus at six out of seven sites from where sewage had been collected in mid-March. Australia’s National Science Agency reported in April that the virus had been detected in two wastewater catchments in Southeast Queensland. It published a paper estimating the presence of 171-1,090 infected people in the region.
This makes WBE a sensitive way to predict the pandemic. It is cheaper than individual testing. On the flip side, WBE can’t pinpoint where an infected person lives.
Barriers in India
This said, in India, there is a reluctance to test sewage for the novel coronavirus. A source close to the Indian Council of Medical Research (ICMR) said, “COVID-19 is a respiratory infection and the role of sewage in its transmission or understanding the dynamics of its epidemiology is likely to be extremely limited, if any.”
A few water utilities have tested sewage and found the virus, but have stopped short of widespread, continuous testing required for disease surveillance. Chennai MetroWater was among the first water-supply agencies in the country to conduct a preliminary study, in early May, when it detected traces of the virus in wastewater. The utility collected two samples each from areas that had COVID-19 patients and those free of any cases. Traces of the virus were found in samples from the former locations. The agency planned to develop a protocol to test sewage for the virus, with help from the WHO.
However, a few weeks later, ICMR reportedly stopped the study. ICMR had asked the governments of New Delhi, Maharashtra, Karnataka, Andhra Pradesh, Uttar Pradesh, Rajasthan and Madhya Pradesh to take up similar studies. The idea was to develop a protocol and standard operating procedures. That was a month ago. Emails to ICMR elicited no response.
Researchers from IIT Gandhinagar also began testing sewage in May and found traces of the virus. They are working with about 50 research organisations to develop a systematic way to test. Manish Kumar, who is leading the work, said wastewater is an important source to monitor the presence and progress of the infection because both symptomatic and asymptomatic individuals’ excreta has the virus. But the city’s municipal corporation hasn’t been cooperative.
Other developing countries are also sitting on the fence. Agua y Saneamientos Argentinos (AySA), Argentina, teamed up with Aguas de Murcia, Spain, to understand how to test sewage for the virus. Their combined results: viruses have been found but AySA engineer Alejandro Barrio said they have so far not been able to successfully isolate the virus from sewage because it is highly contaminated.
Malaysia’s water utility, the Indah Water Konsortium (IWK), is not monitoring wastewater for the virus for want of testing kits. Its staff had collected wastewater samples and they are pending testing, according to chief engineer S. Velayutham. Meanwhile, IWK is monitoring its workers at wastewater treatment plants to make sure they are not infected.
In Uganda, the National Water and Sewerage Corporation has not yet started testing for the virus in sewage. Instead, the Kampala Capital City Authority has, led by the Ministry of Health, prioritised worker safety, like their Malaysian counterparts. They are studying the link between wastewater monitoring and identifying COVID-19 hotspots.
Over the past few weeks, more testing has pushed up the numbers of COVID-19 patients. These are done in a controlled manner. Testing sewage will doubtless lead to a major jump in prevalence rates. Those affected by the virus shed it in their stools typically five days after exposure, and continue doing so for four weeks or so.
So looking for, and then finding, the virus in our sewers could complicate attempts to control the public narrative and impression of India’s COVID-19 epidemic. At the same time, from international experience, it does seem testing sewage will be cheaper and could faster predict COVID-19 outbreaks. Such efforts can also easily be adapted to Indian conditions.
Nitya Jacob is a water policy analyst and the director of policy at Swasti.