Dr. Rakesh Mishra, Director, TIGS, explains the significance of the low-cost but efficient wastewater surveillance technique.
Researcher drawing water from STPs for wastewater surveillance (#COVIDActionCollab)
The Covid-19 pandemic has already claimed millions of lives worldwide, and the threat is far from over. The virus is still mutating, and the need of the hour is to track new sub-variants and pathogens, besides introducing new surveillance techniques.
One such technique — crucial but low cost — is wastewater surveillance.
Speaking to South First, Dr Rakesh Mishra, director at the Tata Institute of Genetics and Society (TIGS), Bengaluru, and former director at the Center for Cellular Microbiology (CCMB), Hyderabad, explained this low-cost but effective technique.
After the first Covid-19 wave, Mishra started wastewater surveillance in Hyderabad and later expanded it to Bengaluru, where he is now based.
He also elaborated on how civic departments in our cities can help in identifying viruses and pathogens early and thereby prevent an outbreak.
Wastewater surveillance is a convenient way of knowing what is happening in a city, in terms of infection, medicine usage, drugs, etc.
Dr. Rakesh Mishra
“Everything eventually comes out through the sewage system,” Mishra said.
Viruses or pathogens enter wastewater through the stool of infected people. Scientists can test the sewage treatment plant (STP) samples for pathogens.
“By testing, we know how many viral particles an infected person is shedding in a day. We also try to get the population size in the STP’s catchment area and estimate the RNA (Ribonucleic acid) fragments of the virus in the sewage system,” he explained.
‘This helps in estimating the number of people shedding the virus. With this data, we can calculate the number of infected people in the catchment area on that particular day,” Mishra added.
Wastewater surveillance provides community-level data quickly and efficiently. Wastewater data can show changes in disease trends four to six days before those signs are reflected in clinical cases. A single wastewater sample captures the infection status of a population numbering thousands to millions of individuals.
The World Health Organisation (WHO) declared India polio-free in 2014. But one case of vaccine-derived poliovirus (VDPV)-type 1 was detected in a sewage sample in Kolkata on 25 April, 2022.
This was made possible after WHO’s wastewater surveillance detected the virus that has not been reported in India since 2011.
Wastewater surveillance is not new. It has been carried out for a long time but on a smaller scale. “It gathered pace during the pandemic, and its benefit caught the attention of several civic agencies,” Mishra pointed out.
He added that the number of infected people in a city can be estimated by testing samples collected from the STP for a few thousand rupees. “We are taking about several lakhs of people living in and around the city.”
Mishra’s team has been testing many pathogens, including that dengue, Covid-19, and tuberculosis. “We can detect various serotypes of dengue and tuberculosis. We even tried to track monkeypox, but it was not present,” he said.
As of August 2022, the initiative has started testing wastewater for viruses Influenza A, Influence B, H1N1, monkeypox, and degraded SARS-CoV-2 RNA.
During the first Covid-19 wave, Mishra and his team surveilled wastewater in Hyderabad. After retiring from CCMB, he joined TIGS in Bengaluru, where he continues tracking viruses and pathogens present in wastewater.
“Since last year, we are carrying out extensive surveillance in Bengaluru with the cooperation of the Bruhat Bengaluru Mahanagara Palike (BBMP). The BBMP has allowed us to collect samples from wastewater tanks, and the Palike even shares patient samples with us for analysis,” he said, pointing at what civic bodies can do to prevent the spread of the virus.
“We are monitoring all the 28 STPs in Bengaluru every week. After determining the viral load, we inform the Palike about the areas where the viral load is on an uptick and where it is sliding,” Mishra said.
The information is passed on to the BBMP before a virus or pathogen starts infecting people. With the information provided in advance, the civic body can control the spread of the infection or be prepared for a surge in that particular area.
“Testing helps us to know a week in advance if the peak will hit a particular area or not,” Mishra averred.
“This technology is so powerful that we are constantly checking for the variants of SARS-CoV-2, the virus that causes Covid-19, in Bengaluru and Hyderabad. We know exactly which variant and in what proportion,” he said.
“We may not be able to pinpoint the affected individual. But we can estimate the number of affected people. If a hundred people are infected, we can say 50 are carrying this particular variant and 20 are carrying that variant, and so on. Overall, you have an idea of what is happening in that area,” Mishra added.
Even if people are asymptomatic and are not visiting the hospital for treatment, we can detect the presence of the parasite, and that might create a problem. When we have this knowledge, the civic body can be prepared.
“Regardless of the research you do, it won’t have any value unless the system, the regulatory body, and the people accept it,” Mishra said.
The BBMP is cooperative and has provided access to STP sites for collecting samples. “They don’t hesitate to ask about the number of cases detected; they are not scared if Covid-19 cases are quite high in these STPs. We are allowed to put the data on the website, where we upload the cases every week. This has helped the city and civic body know the upcoming trend. They find out the reason and take control of those things,” he added.
What about the Greater Hyderabad Municipal Corporation (GHMC)? “We faced difficulties with the GHMC,” Mishra did not hide his disappointment.
Initially, GHMC provided the team access to STPs and shared the details of the cases. “They (GHMC) got worried over the high number of cases. You cannot deny the truth. You should face the truth,” he added.
Sewage or environmental surveillance is to estimate the exact number of parasites in cities, which means the exact number of people hosting different parasites.
Going forward, the ideal plan should be to make these tests robust and set a Standard Operating Procedure (SOP), so that anyone could use them.
“Open drainages are common in almost all cities in our country. We are in the process of preparing SOPs for open drainages, along with design models for big cities and small cities. In Hyderabad we are surveilling some 20-odd open drainages in collaboration with the CCMB,” Mishra revealed.
The SOP includes standardisation of the timing of collection of samples, frequency of collecting samples, how to determine the concentration, etc.
The Rockefeller Foundation has funded the wastewater water surveillance project of TIGS scientists with $9.5 million for three years.
“One year is over. We are conducting tests in four cities, Hyderabad, Bengaluru Pune, and Delhi,” he added.
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