New Delhi, April 16
A slew of countries, including Australia, South Africa, New Zealand, the US and Canada, are increasingly turning towards analysing sewage water, which plays an increasingly critical role in monitoring transmission of Covid virus and its variants within communities.
Monitoring of wastewater for Covid virus began in late 2020, after several studies pointed out that sewer slime can accumulate SARS-CoV-2 RNA. It is because traces of SARS-CoV-2 can be isolated from what we flush down the toilet — and sometimes survive up to several days after leaving an infected person's body.
According to New Zealand's Institute of Environmental Science and Research, RNA from the SARS-CoV-2 virus was detected at all but one of the 120 wastewater sites from the week to April 10, NZ Herald reported.
The data showed that early in the year, just about 10 per cent of the sites reported quantifiable amounts of virus. By mid-February, it shot to more than a quarter, and around mid-March, it was present in about 90 per cent of them.
The latest data shows how daily cases in the region have tumbled to around 14 per cent of the peak — fewer than 100 daily cases per 100,000, the report said.
Health authorities at Victoria in Australia detected the BA.4 or BA.5 sub-variant of the Omicron strain of Covid in wastewater samples taken from the Tullamarine catchment, ABC news reported. Wastewater testing in March revealed BA.2 had become the dominant strain in Victoria.
A report from the South African Medical Research Council revealed that the analysis of wastewater samples in South Africa shows an increased incidence of Covid-19 in three provinces – Gauteng, eThekwini in KwaZulu-Natal and Bloemfontein in the Free State.
Samples from wastewater plants in Johannesburg and around Pretoria also show that Covid-19 fragments are increasingly common. The Omicron variant dominates all samples so far sequenced with the delta variant found in isolated samples, the report revealed.
"Wastewater is completely independent of whether you get tested or not – everybody poops," Mark Servos, a professor at the University of Waterloo in Ontario, was quoted as saying to CTVNews.ca.
"Wastewater is really one of our only reliable tools to determine what's going on in terms of community prevalence."
As of April 2, the Canadian city of Waterloo's weekly average for the number of N-gene copies (well-preserved in wastewater) per millilitre was about 415, representing a steady increase in Covid-19 concentration levels since mid-March.
A large driver of this growth has been the rapid spread of the Omicron BA.2 sub-variant within the province, Servos said.
"We've now seen that BA.2 is almost 100 per cent in most of the wastewater [samples] that we've been studying," Servos added.
Other provinces like Alberta and British Columbia are also seeing a rise in Covid in wastewater samples.
About a third of wastewater sampling sites across the US have shown an uptick in Covid-19 cases across the country, according to latest data from the US Centres for Disease Control and Prevention (CDC).
