The results of a seroprevalence study conducted in Chennai between mid-July and early August have shown that overall, one-fifth of the population in the City was exposed to SARS-CoV-2 infection.
The study was done by the National Institute of Epidemiology of the Indian Council for Medical Research here along with Greater Chennai Corporation. The preliminary findings of the report indicated that around 80% of the population was still susceptible to the infection in the City. The study was done to estimate seroprevalence of SARS-CoV-2 infection in general population aged 10 years or higher in the Greater Chennai Corporation and to determine sociodemographic risk factors for SARS-CoV-2 infection in the city.
Noting with concern a huge variation in seroprevalence across zones — they range between 7.1% in Madhavaram and 44.2% in Tondiarpet — the report said there was a need to understand the reasons for this in order to improve the control measures.
Blood samples from 12,405 individuals from 51 wards covering all the 15 zones of the GCC were collected, and analysed in the lab. A total of 2,673 individuals had evidence of past SARS-CoV-2. The infection to case ratio, calculated by dividing the estimated number of infections by total number of COVID-19 cases reported 1 to 2 weeks before the survey, was lower than some of the published studies, the results said, indicating high testing.
The infection to fatality ratio, arrived at by dividing the number of deaths reported three weeks after the survey by the estimated number of infections, was comparable or lower than other published studies, the preliminary findings added.
