In Covid fight, India could learn from polio experience
New research suggests that testing sewage with traces of Sars-Cov-2, the virus that causes Covid-19, could indicate the spread of the disease in a population.
India’s battle-tested system of environmental surveillance of wild polioviruses in municipal wastewater may be leveraged to detect the coronavirus disease (Covid-19) among local communities, experts say.
New research suggests that testing sewage with traces of Sars-Cov-2, the virus that causes Covid-19, could indicate the spread of the disease in a population. A study published in the science journal Lancet on April 1 said the virus was being discharged in the faeces of people five weeks after their respiratory samples had tested negative for Sars-Cov-2.
Studies also record persistent shedding of virus genetic material ribonucleic acid (RNA) in human excretions like stool, saliva, sputum and urine, which find their way into the sewers.
“One of the sturdier components of a virus is its RNA, which remains in wastewater even after the virus is not viable,” said Swapneil Parikh, an internist at Kasturba Gandhi hospital and co-investigator for the Brihanmumbai Municipal Corporation’s (BMC) convalescent plasma trials in Mumbai.
The BMC is close to launching a pilot environmental surveillance programme in Mumbai, based on a proposal submitted by Parikh and other experts, which was approved by Maharashtra minister Aaditya Thackeray earlier this month, according to Parikh.
“Protocols for the same are yet to be validated, but have been taken up by the health ministry and a WHO expert team. Once they have shared the methodology, we can start the exercise, perhaps early next week,” he said.
This real-time monitoring of sewage can help detect and contain Covid-19 infections early, experts said.
“In theory, it can be re-purposed to track the Sars-Cov-2 virus in wastewater,” said Giridhara Babu, head of lifecourse epidemiology at the Public Health Foundation of India. “While it is still a theoretical possibility because the viruses themselves are dissimilar, there is work being done globally to fill the evidence gaps. To implement this in India, the National Institute of Virology would have to first validate a standardised protocol for monitoring of Sars-Cov-2 in wastewater.”
Pankaj Bhatnagar, acting team lead on India’s National Polio Surveillance Project, said, “The methodology and testing protocols for detection and isolation of poliovirus from municipal waste water are being applied following standardization after years of research. Since the poliovirus and Sars-CoV-2 have dissimilar biological characteristics, the laboratory testing protocols for detection of Sars-CoV-2 in waste water are different and are still evolving. “
Bhatnagar also clarified that research around this issue is still nascent, and that there is currently no conclusive evidence to support such a proposal.
The required evidence is being pursued by researchers globally,including those at the Indian Institute of Technology (IIT) Gandhinagar, which is part of the Covid-19 WBE Collaborative, an international project launched by 51 universities and research institutes. The consortium, a partnership between Sewage Analysis CORe group Europe (SCORE) and the Global Water Pathogen Project, has laid out a standard protocol to ensure uniformity in data collection and inference.
“While case finding by testing human subjects is important, it would be beneficial to complement it with a wastewater based epidemiology approach, which is less invasive and less financially demanding. It has been well documented that wastewater surveillance can be leveraged to control the spread of infectious diseases,” said Manish Kumar, an assistant professor at the department of earth sciences, IIT Gandhinagar, and one of the consortium’s collaborators.
In India, WBE played a vital role in the eradication of polio in 2011. India continues wastewater surveillance at 52 wastewater treatment plants and unregulated catchment areas where sewage is drained in nine states and one Union territory.
By testing these sites weekly for traces of wild polioviruses, the authorities were able to launch preventive immunisation drives in affected areas. In 2018, for example, when traces of a wild poliovirus strain were detected in sewage in Mumbai, the findings resulted in widespread immunisation campaigns to prevent an outbreak.
“There is certainly merit in both leveraging India’s environmental surveillance for polio as well as the larger system for polio monitoring. At a state and district level, medical officers have excellent training and there is good data management. I don’t know the extent to which the manpower and expertise will be co-opted in the effort against Covid-19, but they can be valuable resources,” said a member of the National Certification Committee for Polio Eradication, requesting anonymity.
Babu and Kumar stressed that environmental surveillance for Sars-Cov-2 is by no means a replacement for individual case findings, or any other mode of public health surveillance.
“Environmental surveillance can be successful only when complemented using sentinel surveillance, hospital admission data, prescription data, human bio-monitoring, and mortality and morbidity data to create effective responses,” said Babu, who was a part of the World Health Organisation polio team in Karnataka for six years.
“India would have a significant advantage over other countries in using such environmental surveillance after our experience with polio. If we can fine tune our methodology to monitor for Sars-Cov-2, it would benefit other parts of the world too,” he said.