In Bengaluru alone, 1000’s would have been contaminated by XBB.1.16.
| Photo Credit: The Hindu
The XBB.1.16 Omicron recombinant first detected in India on December 25, 2022 has turn into the dominant variant in the nation. Based on 2,856 genome sequences from India posted on GISAID between December 1, 2022 and April 8, 2023, a staff led by Dr. Rajesh P. Karyakarte, Head of the Microbiology Department on the BJ Medical College, Pune discovered that the XBB.1.16 lineage had grown from 9.3% in the primary week of February to 79.17% in the primary week of April. The outcomes of the study, which is but to be peer-reviewed, was posted on medRxiv preprint server.
The variety of circumstances in India detected via RT-PCR testing started to slowly rise in the primary week of March and reached a peak on April 19 with 12,591 infections and a every day check positivity price of 4.39%. With every day testing remaining very low, the variety of circumstances detected doesn’t replicate the precise unfold of the XBB.1.16 variant.
In distinction, environmental surveillance carried out by testing sewage water samples from 28 sewage remedy crops unfold throughout Bengaluru by the Tata Institute for Genetics and Society (TIGS) has revealed the true extent of unfold of the virus in town. One pattern collected as soon as a week from every of the 28 remedy crops reveals that RNA fragments discovered in the sewage water started rising from early-March and peaked on April 1.
At its peak, over 80,000 virus copies per ml have been current in town. That would imply that 1000’s of individuals have been contaminated in Bengaluru alone.
Wastewater samples
“We find only RNA fragments of the virus and not the virus particle itself in wastewater samples. Since one infected individual can shed 10 million copies, it is possible to calculate the number of infected people by taking into consideration the total volume of wastewater treated in each plant,” says Dr. Rakesh Mishra, director, TIGS, which has been endeavor environmental surveillance of SARS-CoV-2 in Bengaluru since August 2021.
“It appears that Bengaluru witnessed an invisible wave of COVID-19 that was far bigger than the third wave driven by BA.1 and BA.2 Omicron variants in January 2022,” he says. And this should be the case throughout India as XBB.1.16 had unfold throughout the nation in March-April. There was one other silent wave in Bengaluru in June 2022 pushed by one of many Omicron variants.
“Since the treatment plants are spread across Bengaluru, we can tell which area of the city has a greater number of infected people by measuring the pathogen load. Wastewater surveillance can provide a granular picture of infections in the city. And this will help in advising and cautioning the civic authorities about any new variant or increase in infections even when it is not apparent,” he says.
Reluctance
Not solely has every day testing numbers dropped sharply, folks have turn into reluctant to get examined even when signs are apparent. In many cases, the contaminated stay asymptomatic.
Wastewater testing is an energetic type of environmental surveillance, and has been in place for many years in the case of polio. It supplies a pretty correct measure of pathogen load in the wastewater and by extension, the extent of virus unfold in the neighborhood. The greatest benefit is that wastewater surveillance doesn’t require contaminated folks getting examined nor testing amenities to be in place. Testing of wastewater for RNA fragments can be pretty simple.
“We share the results of wastewater surveillance with the civic authorities (BBMP) every week. We have been able to undertake this surveillance due to the willingness of the civic authorities,” says Dr. Mishra. “With the SARS-CoV-2 virus here to stay, and the virus continuing to evolve, it is essential to undertake environmental surveillance in every city in the next one-two years.”
