1/3 of TN’s population was exposed to coronavirus: Serosurvey
Express News Service
MADURAI: Nearly one third of the State’s population (31.6%) had been exposed to coronavirus, reveals the statewide sero-survey conducted on 26,135 samples by Department of Health and Family Welfare across 37 districts in October-November 2020.
In Chennai, the seroprevalence was 40.94 per cent. The State Health Department conducted the first phase of the statewide sero-survey in 37 districts by collecting blood samples (5ml each) from 2,640 randomly selected participants (aged above 18 years) in 888 clusters (comprising 30 participants in each cluster) during October 19 - November 30 last year.
Of the 26,640 samples collected, 26,135 were found fit for the study, while 505 samples were deemed unfit due to reasons including inability to obtain lab results, ineligibility of testing criteria, incomplete details of participants and disproportionate clusters (less than 30 participants in a cluster), states the report on the sero-survey, which was accessed by Express. The samples were classified on the basis of gender, habitat (urban/rural), age and districts. The blood serum thus collected were tested through chemiluminescence immunoassay (CLIA) technique.
Speaking to Express, Dr TS Selvavinayagam, Director of Public Health and Preventive Medicine and co-author of the study, shared, “The findings of the sero-surveillance indicate that nearly one-third (31.6%) of Tamil Nadu’s population had been exposed to coronavirus at the time of the seo-survey (October-November, 2020). The survey results also imply that, in a State with a population of approximately 7.2 crore, at least 2.2 crore were infected by November, which is roughly 36 times the number of patients who tested positive for Covid through RT-PCR tests.”
The estimated seroprevalence indicates an infection fatality rate of 0.052 per cent, the study, published in medRxiv, an internet site that distributes unpublished e-prints about health sciences, observed. According to the yet-to-be-peer-reviewed study, among the 37 districts, the highest of seroprevalence (percentage of individuals with antibodies against Covid-19) was found in Perambalur district at 51.05 per cent, while the lowest was found in The Nilgiris at 11.1 per cent. Consistent with the higher density of population in urban areas, urban residents were found with higher exposure to the virus at 36.9 per cent seroprevalence, while it was 26.9 per cent in rural parts.
Further, the exposure to the infection was noticed to be higher at 31.6 per cent among those aged 40-49, while the seroprevalence in the age group 18-29 was lower at 30.7 per cent and the elderly aged more than 70 years at 25.8 per cent, which is significantly lesser. Dr J Radhakrishnan, Principal Secretary to the Department of Health and Family Welfare, stated that efforts were underway to publish the findings of the sero-surveillance as an academic research paper in a reputed medical journal of international standards. Public health expert and former Director of Public Health Dr K Kolandaswamy said that by now the seroprevalence would have been 40 percent in the State.
(With inputs from Chennai)
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