The second serological survey in the city has found that one-third of the population has been exposed to the SARS-CoV-2 infection and has developed antibodies.
According to the Greater Chennai Corporation, of the 6,389 samples tested, 2,062 were positive for the presence of IgG antibodies, recording an overall positivity of 32.3%.
In fact, the first serological survey, the results of which were released in early September, found that one-fifth of the population in the city was exposed to the infection.
Meanwhile, the Directorate of Public Health (DPH) and Preventive Medicine has launched a State-wide serosurvey with a sample size of 26,640. According to a press release, the population-based serosurvey had been taken up across cities and villages in the State.
A total of 888 clusters have been identified for the survey. In each cluster, the survey would cover 30 houses, collecting details and blood samples from 26,640 persons in total. It would screen the samples for the presence of antibodies against COVID-19.
District-wise enumeration
An official said the sample size was determined based on the population of the district. These samples would be tested in the State Public Health Laboratory in Chennai and other public health laboratories in Coimbatore, Salem, Tiruchi, Madurai and Tirunelveli. For this, high-end laboratory equipment worth ₹4 crore would be put to use. Chemiluminescent immunoassay technique would be used for the test.
Public health teams were formed and trained to identify persons and take up testing in every district.
The process would be completed by the second week of November. The survey was jointly taken up with IDFC, Mumbai, through a memorandum of understanding.
At the end of the survey, the average number of persons affected by COVID-19 in the State would be enumerated at the level of each district.
The findings of the survey would help the State government and the Health Department in coming up with policies, the release said.
