Seroprevalence of SARS-CoV-2 infection has been higher among women in Chennai, with 23.7% of the 6,493 women exposed to the infection, as per a serosurvey conducted in July.
According to the serosurvey, 19.3% of men have been exposed to the infection in the city. Of the 5,785 men who participated in the serosurvey in Chennai, 1,115 were exposed to the infection. Just 12.2% of individuals of the third gender have been exposed to SARS-CoV-2 infection.
Nearly half of the cases in Tamil Nadu have been reported from Chennai. The number of cases have been increasing since May 2020. Following the rising trend of reported cases, an intense lockdown was imposed in the city from June 19, 2020.
The objective of the serosurvey was to estimate seroprevalence of SARS-CoV-2 infection in a general population aged more than 10 years in Chennai. The serosurvey data would be also used to determine socio-demographic risk factors for SARS-CoV-2 infection in the Greater Chennai Corporation, covering 426 sq km and spanning 15 zones.
The sampling procedure of the serosurvey included the selection of 50 of the 200 wards by population proportion to size method, and the selection of six streets from each ward by simple random sampling.
According to the serosurvey, Korrukkupet registered the highest seroprevalence with 50%. Areas such as New Washermenpet, Royapuram, Royapettah, Egmore, Pulianthope and Kaladipet have also registered high seroprevalence in the city. But Lakshmipuram in Madhavaram has registered only 2% seroprevalence.
Raja Annamalaipuram has registered a seroprevalence of 25%. Seroprevalence in Chetpet is 22%, Saidapet 23%, Thiruvanmiyur 16%, Anna Nagar 15%, Teynampet 33%, West Mambalam 15% and Saligramam 10%.
The estimated number of infections was the highest in Royapuram with 2.99 lakh persons infected.