In the case of the Coronavirus pandemic, where every wave seems to take the citizens and government by surprise and storm, this method could work as a default alert system for the government bodies to immediately restrict the movement of the local population and tighten containment zones. Scientists around the world have long used the technique, known as wastewater-based epidemiology (WBE), to track social scourges such as drug use or chemical spills with the aim to guide policy decisions. An outbreak of polio in Israel in 2013 was detected by the monitoring of sewage. India, too, has its wastewater surveillance methodology to thank for eradicating the polio virus, which spreads through water. Dr Mohan explains: “It’s fairly simple. This technique involves researchers initiating an intensive wastewater surveillance study by collecting sewage samples at regular intervals. These are then packed in a disposable pack to avoid leakage during transportation. Isolated RNA is then quantified using an RT-PCR detection kit.”

S Venkata Mohan

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His team identified a total of five lakes in Hyderabad for the study: Hussain Sagar, Nacharam lake, Nizam Talab, Edulabad lake and Potharaju lake. The report, published in medRxiv earlier this month on May 12, states: “In this work, we monitored urban, peri-urban and rural lakes in and around Hyderabad as a long-term surveillance study for the presence of enteric virus SARS-CoV-2 gene fragments. The study time of seven months coincided with 
the first and second wave of Covid-19 infection.”

Hussain Sagar: The Hyderabad team monitored five lakes for seven months and found that viral load was higher in three urban lakes

The study titled, Comprehensive and Temporal Surveillance of SARS-CoV-2 in Urban Water Bodies, depicted differential viral RNA copies in the urban lake with high viral load observed during the peaks of the first and second waves of the pandemic. 

Nacharam Lake

Dr Mohan says monitoring was done at every site once a month from July 2020 to April 2021. In November 2020, the sites were monitored four times a week. “We found that the viral load was initially stable. It then shot up. This was during the first wave. It went down, and then upped again in February 2021, indicating the onset of a second wave. And that is exactly how things unfolded on ground. A second wave did arrive in the country in late March 2021, validating our paper,” Mohan says. 

Also Read: Mumbai: 50 per cent active Covid-19 case load in western suburbs

Nizam Talab

In March 2020, a similar study was conducted in New York, initiated by environmental epidemiologist Dr David Larsen. “Back then, scientists in the Netherlands had shown proof of the concept that SARS-CoV-2 RNA can be pulled from wastewater. At the start of the pandemic last year, our case-based surveillance system was inadequate to identify communities without SARS-CoV-2 transmission, and the result was a state/nation-wide shutdown. Wastewater surveillance, on the other hand, would have rapidly and cost-effectively characterised the spread of SARS-CoV-2.”

Edulabad Lake

A report he published in September 2020, argues that wastewater surveillance of Covid-19 has many benefits. In an email interview to mid-day, Dr Larsen says, “The method of tracking infectious diseases in wastewater is more than 150 years old. It was first used by John Snow during the cholera outbreak in London, where he tracked the contamination in the broad street pump to an adjacent leaking cesspool. Until now, epidemiologists have primarily thought of wastewater surveillance as a tool to survey waterborne or fecal-oral transmitted pathogens. But lots of pathogens can be found in wastewater, including HIV and tuberculosis. I have the feeling that most infectious diseases could be surveyed via wastewater.”

Wastewater from Wadala sewage treatment plant flows into the Antop Hill area. The ICMR-NIV team had collected samples from this site for their study, which was published in March 2021. Pic/Ashish Raje

But, Covid-19 is fueled by respiratory droplets. How is it then found in stool samples? This is not entirely surprising, thinks Dr Larsen. “The SARS-CoV-2 RNA found in the stool is non-infectious. It is the dead cells and dead virus that the body is shedding naturally. A wastewater surveillance network carries three major pieces of information: if the virus isn’t found, it can give an indication of a community free from transmission. It can provide an early warning of increasing transmission, and it can also help track the trajectory of transmission in a community, alerting to increasing or decreasing transmission.”

The CSIR-IICT team, led by S Venkata Mohan, collects water sample from Tarnaka  open drain in Hyderabad

Interestingly, a similar study was proposed by internal medicine specialist and healthcare entrepreneur Dr Swapneil Parikh in Mumbai, when the pandemic struck last year. Parikh says the BMC was unable to take up the proposal due to lack of funds. “We must understand the importance of this technique of surveillance in the pandemic. If researchers start sequencing the sample water, it can also determine which variant of SARS-CoV-2 is spreading in the local community. I believe it is critical that we start monitoring our sewage. India already has a rich history of doing this to detect polio virus. We can use a similar methodology to track Covid-19 infection,” Dr Parikh says.

David Larsen and Deepa Sharma

Mid-day learnt that a study in this direction is being done by the National Institute of Virology (NIV) in collaboration with the Indian Council of Medical Research (ICMR). Published in March 2021 on the Indian Journal of Medical Research, this report is titled, SARS-CoV-2 detection in sewage samples: Standardisation of method and preliminary observations. Dr Deepa Sharma, in-charge polio surveillance, ICMR-NIV, Mumbai unit, is one of the authors of this study. “Before the pandemic struck India, our team was already collecting water samples for the polio virus. This is an ongoing procedure to ensure no new polio cases are detected in the population. In February 2020, we found that Netherlands had reported the presence of SARS-CoV-2 RNA in sewage samples. That quickly set things in motion here,” she says. 

Dr Deepa’s team began using wastewater samples collected for polio detection to look for the presence of SARS-CoV-2 RNA. This exercise went on till May 2020. “Sewage specimens were collected from six sites in Mumbai—Wadala (F north ward), Dharavi (G north ward), Kurla (L ward), Shivaji Nagar (M east ward), Malad (P north ward) and Kanjur (S ward). We found that all the samples collected before March 11, 2020 (when the first Covid-19 positive case was found in Mumbai) were SARS-CoV-2 negative. However, viral RNA was detected in sewage samples collected during May 11-22, 2020 in all the six wards.” 

It would be feasible to initiate sewage surveillance for SARS-CoV-2 to generate data about the viral transmission in various epidemiologic settings, the study concluded. The ICMR-NIV team is now planning to publish a second paper on their research, post which the BMC will take a call on setting up a surveillance project in the city.

Virendra Sharma, Texas-based expert in environmental health, says that wastewater epidemiology was also conceptualised as a method to determine the presence of different drugs in 2001 (conceived by Christian Daughton) and performed by Ettore Zuccato in 2005 for cocaine use in a community. 

Eric Lichtfouse

Eric Lichtfouse, professor of environmental chemistry and scientific writing at Aix Marseille University and Xi’an Jiaotong University, calls this the ‘biomarker approach’. “As environmental chemists, we knew from past studies that wastewater contains interesting information in organic molecules called biomarkers. These molecules come from the faeces and waste of thousands of people. For instance, if you eat antibiotics to cure a disease, some of these antibiotic molecules will end up in wastewater too. The unique advantages of this approach is that you can get critical information much faster than you would by analysing thousands of individual persons. Therefore, we conducted a survey of recent publications on Covid-19 in wastewater, and found indeed that Covid-19 can be detected earlier in wastewater compared to testing individuals. This is critical information in order to take early measures, and save lives,” Lichtfouse adds.

Lichtfouse is currently based in France, where wastewater is monitored daily in major cities. He says, “In India, the government needs to monitor all wastewater plants daily [or more frequently] to follow the increases or decrease in viral loads, and the type of variants present. This should help the government to take appropriate measures.”
 
On May 2, the European Union (EU) called on member states to monitor wastewater to detect COVID outbreaks early. Some European countries have already begun monitoring sewage systems and were able to forewarn about worsening outbreaks. “It is crucial that EU countries set up effective wastewater monitoring systems as soon as possible and ensure that the relevant data is immediately made available to health authorities,” Environment Commissioner Virginijus Sinkevicius told a German newspaper.

Now, even the Centers for Disease Control and Prevention (CDC) and the US Department of Health and Human Services (HHS), in collaboration with agencies throughout the federal government, are initiating the National Wastewater Surveillance System (NWSS). 

And if all of this sounds dense, check out COVIDPoops19. Colleen Naughton, professor at the University of California, has been making a big difference with a small Twitter account. In May 2020, she created the comical account to tweet findings on Covid-19 and SARS-CoV-2, after universities across the globe began testing wastewater. Naughton’s lab finds the latest information by scouring Twitter, credible publications, news articles and webinars and adds it to the CovidPoops19 dashboard. The dashboard was made possible through an emergency seed grant from the Center of Information Technology Research in the Interest of Society (CITRIS). Naughton also recently received funding through Michigan State University and the Bill & Melinda Gates Foundation to continue the work. 

2005
Year in which waste water epidemiology was used to detect use of illicit drugs in various locations. Since then, it has been used as early detection method for viral outbreaks