The serosurvey study that was carried out by the National Institute of Epidemiology for the Greater Chennai Corporation has shockingly revealed that the 20% population of the city had been exposed to the COVID-19 viral infection till the second week of July. 

The study has aimed to capture the grounds of exposure of the pandemic in the city. Serosurvey has been defined as a test of blood serum that was collected from a group of individuals to determine the seroprevalence and this will be used to monitor the trends in the prevalence of the COVID-19 disease at the district level and the survey will also put out the community transmission in any part of the country. 

According to the reports, the blood samples from 12,405 individuals from 51 wards across all the 15 zones in Chennai were collected between July 18 and July 28 to find out the exposure of the global pandemic in the city. Following the collection, the samples have proceeded for testing on August 6 for IgG antibodies against the viral infection. IgG or Immunoglobulin G antibodies would be appearing in the human body by the end of the first week of an individual who got infected by the virus. 

The results have come and as per the results of the survey, of 12,405 individuals tested, 2,673 individuals had evidence that they had got a COVID-19 viral infection with a seroprevalence of 21.5%. Experts say that if this survey taken larger to the population of Chennai, it suggests that over 15.26 lakh people in Chennai have been infected by the COVID-19 viral infection.  Chennai's population is 82.16 lakh and as per the survey, at least one-fifth of the city's population has been exposed to the global pandemic. 

The survey results that were released on Tuesday stated that around 80% of the population is still vulnerable to the pandemic. According to the survey, of 15 zones in Chennai, 44.2% of those tested had been exposed to the COVID-19 viral infection in the Tondiarpet zone which is highest in the city while the Madhavaram zone had reported the least exposure with only 7.1% of those tested had exposed to the pandemic. 

Following Tondiarpet, Royapuram had reported the second-highest exposure with 34.4% followed by Thiruvottiyur (31.6%), Teynampet (29.4%), Anna Nagar (25.2%), Manali (24.1%), Thiru Vi Ka Nagar (22.1%), Adyar (17.3%), Kodambakkam (14.9%), Valasarvakkam (14%), Ambattur (13.5%), Alandur (11.1%), Shollinganallur (10.3%), and Perungudi (7.3%). 

The survey had also revealed that among those tested, more women (24%) had the presence of IgG antibodies than men (19%). The study had further shown that seroprevalence was as high as 65% among those with a history of respiratory symptoms. Speaking about the survey, Chennai Corporation Commissioner Prakash said that survey had helped the civic body to refocus its health interventions. 

By citing that the zones with high seroprevalence had seen the cases decreasing, the commissioner stated that the city is attaining the stability and stated that the efforts would be intensified in zones where the seroprevalence was lower. The commissioner further added that the study was done in July and said that many more could have obtained immunity since then and the civic body would continue with more such surveys.