Covid RNA Found in Sewage Samples from Delhi, Mumbai | How Testing Wastewater Helps Contain Pandemic

Union Health Minister Mansukh Mandaviya on Saturday said SARS-CoV-2 RNA has been detected in sewage samples from Delhi and Mumbai and the Centre is working in “alert mode” to contain the spread of Covid-19 infections in the country.

Amid concerns following a surge of Covid-19 cases in neighbouring China, Mandaviya said, “We are working on alert mode to control the spread of Covid-19 and conducting environmental, sewage and human surveillance. Virus RNA was found in sewage samples in Delhi and Mumbai. I urge people to wear masks, avoid crowded places and follow Covid-appropriate behaviour.”

The statement came a day after Mandaviya advised states to strengthen the surveillance system for whole genome sequencing of positive case samples to track variants through the Indian SARS-CoV-2 Genomics Consortium (INSACOG) network.

In a virtual meeting on Friday with health ministers and senior officials of states for the Covid-19 situation and preparedness for a likely surge in the country, Mandaviya said: “Focus is to be given to health facility-based sentinel surveillance, pan-respiratory virus surveillance, community-based surveillance, and sewage or wastewater surveillance. (There is a) Need to collectively reinvigorate the system and remove any sense of complacency and fatigue.”

Why Track SARS-CoV-2 RNA in Wastewater?

Environmental surveillance by testing wastewater for evidence of pathogens has a long history of use in public health, particularly for poliovirus. According to the World Health Organization (WHO), the detection of non-infective RNA fragments of SARS-CoV-2 in untreated wastewater and or sludge has been reported in a number of places including Milan, Italy; Murcia, Spain; Brisbane, Australia; multiple locations in the Netherlands; New Haven, Connecticut and eastern Massachusetts, United States of America; Paris, France; and existing poliovirus surveillance sites across Pakistan.

While SARS-CoV-2 spreads mainly via the droplets of respiratory secretions, detection of the active infection of the gastrointestinal tract can be traced in stool samples of patients.

Researchers in the Netherlands, France and the United States of America, demonstrated a “correlation between wastewater SARS-CoV-2 RNA concentrations and COVID-19 clinical case reports; the latter two further suggesting that the RNA concentrations could provide a 4- to 7-day advanced notice ahead of COVID-19 confirmed case data,” WHO said.

Apart from early detection, WHO noted that environmental surveillance has the potential to be used to complement clinical surveillance or monitor areas with poor performance, for example in crowded, extremely low-resource settings such as informal settlements or more generally in marginalised populations.

As a monitoring tool for authorities, such surveillance can aid them to detect unrecognised transmission of SARS-CoV-2 and determine whether Covid-19 has truly been contained in an area.

In India, a study led by scientists at IIT-Gandhinagar in 2020 found that increased “gene copies” of the virus in Ahmedabad’s wastewater matched the incidence of the disease in the city. Researchers noted that as treatment plants collect wastewater across large regions, measuring the level of RNA in untreated wastewater may provide valuable insight into the percentage of people infected within a region.

According to scientists, wastewater-based epidemiology (WBE) was an effective tool during outbreaks of other viruses such as Poliovirus and Hepatitis A.

Delhi and Mumbai Sewage Surveillance

The Indian Council of Medical Research (ICMR) found viral RNA of the SARS-CoV-2 virus in sewage samples from Mumbai in 2021. Under a study done by ICMR’s National Institute of Virology, Mumbai Unit and Division of Epidemiology and Communicable Diseases, New Delhi, a total of 20 sewage samples collected from six different wards in Mumbai city during May 11-22, 2020. Real-time reverse transcription-polymerase chain reaction (RT-PCR) assay was used to detect the presence of SARS-CoV-2 RNA. Viral RNA was detected in sewage samples collected during the ongoing covid-19 pandemic in all the six wards, the authors were quoted as saying by PTI.

On Thursday, Delhi government officials said the National Centre for Disease Control (NCDC) has been collecting sewage samples from seven sites across the national capital and testing them for the presence of coronavirus variants.

Meanwhile, Delhi Chief Minister Arvind Kejriwal has said the new Omicron sub-variant BF.7 which is causing a surge in cases in many countries has not been detected in Delhi so far. He further said his government is fully geared up to tackle any possible surge in cases.

Read all the Latest India News here