The State is all set to conduct a second round of serological prevalence survey in all the 30 districts as well as eight zones of Bengaluru in mid-January.
A serological prevalence survey involves drawing blood samples to detect whether the person was exposed to SARS-CoV-2 in the past and whether he/she has developed Immunoglobulin G (IgG) antibodies to combat the infection.
The first round done from September 3 to 16 had shown that 16.4% of the 16,585 people covered under the survey had developed antibodies and 12.7% had an active infection. The survey — that included people who had COVID-19 infection (prior to the survey) and those who had active infection during the survey — found an overall prevalence of 27.3% in the State then.
Official sources, who are part of the team that is chalking out protocols for the second survey, told The Hindu that the sample size from each district would be increased to around 1,500 this time. During the first survey, an average of 400 samples from every district was included. “The proposal is to cover over 35,000 people from high, moderate and low-risk categories. The protocols have been chalked out and the survey is expected to begin mid-January,” sources said.
“We had expected that the State would witness a surge after Dasara, Deepavali, bypolls and GP polls as there was rampant violation of COVID-19 protocols. But, the surge did not happen and this could be because a large extent of the population may have already been exposed to the virus. The second sero survey will show if this is true and estimate the existing disease burden,” sources said.
The first sero survey had shown that four districts — Dharwad, Gadag, Chickballapur, Bagalkot — and BBMP’s Mahadevapura zone were yet to witness a surge then (September). These districts were found to have the lowest estimated prevalence. The overall prevalence was the highest in Ballari with 43.1% while it was the lowest in Dharwad with 8.7%.
“The second round will reveal if there has been a change in the pattern of the disease spread. We can also ascertain whether the districts with low prevalence then have seen the surge subsequently and if there is a need for further interventions to control the spread,” sources said.
New strain
“In the context of the new mutated variant of SARS-CoV-2, we may also have to consider taking up genome sequencing of random samples that test positive through RT-PCR during the survey. This will help us determine if the new strain is already present in the community. If it is there, we really do not have to worry much,” sources said.
