However, researchers found no viral genome in treated samples of the sites where the virus was detected in untreated wastewater
A recent study by a group of researchers in Jaipur has shown the presence of SARS-CoV-2 viral genome in untreated wastewater samples from the municipal wastewater treatment plants (WWTPs) and hospital wastewater.
This is an important tool to monitor the prevalence and distribution of viruses in a community, especially during a pandemic when limited clinical diagnosis and asymptomatic infections are common.
The scientists who conducted the study are from B Lal Institute of Biotechnology, Jaipur. They collected treated and untreated wastewater samples from different units of six municipal WWTPs over a period of about 1.5 months — May and June, 2020.
They also gathered sewage samples from two major hospitals designated for COVID-19 treatment around Jaipur. The study was published on June 18 in the journal Medrxiv. It is a pre-print paper and non peer-reviewed.
The viral Ribonucleic Acid (RNA) was extracted and subjected to Real Time (RT)-PCR analysis for detection of viral genes from the collected samples.
Two of the samples collected from municipal WWTPs tested positive for viral genes. The scientists further determined whether there was any correlation between the positive samples from WWTPs with the COVID-19 cases reported in the newspapers for the area.
Their analysis showed that soon after the first sampling, there was a continuous increase in the number of COVID-19 patients in the areas served by the WWTPs from where wastewater samples that tested positive for the virus were collected.
The researchers further tested for the presence of viral genome in the treated wastewater samples since this water is used for irrigation in agricultural fields.
They found that no viral genome was present even in the treated samples of the sites where the virus was detected in the untreated samples, thereby validating the efficacy of wastewater treatment systems against COVID-19.
The group claims this is the first study that shows the presence of SARS-CoV-2 from sewage samples in India and provides a basis for developing a warning system where in-person testing may not be available.
Rajasthan had recorded 17,392 confirmed cases and 402 deaths as on June 29, 2020, according to private aggregator https://www.covid19india.org/. Jaipur had 638 active cases as on June 29, 2020.
Environmental surveillance, especially wastewater surveillance has earlier been highlighted as a potential tool to estimate the extent of COVID-19 spread in a particular geographical area.
According to a study published in the journal Emerging Infectious Diseases, the viral RNA begins to be detected in patient samples from the fifth day of illness, with it being present in a few samples even after 30 days of illness.
As a result, the virus can be found in the sewage samples and spread via faecal-oral transmission. In addition to monitoring viral load, wastewater surveillance has been highlighted as an indicator of the presence of drug-resistant bacteria and genes.
At the global level, a Sewage Surveillance Project is being run to estimate the burden of antimicrobial resistance in healthy humans.
The SARS-CoV-2 infection is found to be associated with secondary bacterial infections including those with resistant bacteria. Therefore, wastewater-based epidemiological studies for monitoring antimicrobial resistant bacteria and genes also become important in times of COVID pandemic.
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