Monitoring the trend of SARS-CoV-2 seroprevalence in Chennai, India, July and October 2020

• Published in: Transactions of The Royal Society of Tropical Medicine and Hygiene 2021-11, Vol.115 (11), p.1350-1352
• Main Authors: Kumar, Muthusamy Santhosh, Thangaraj, Jeromie Wesley Vivian, Saravanakumar, V, Selvaraju, Sriram, Kumar, C P Girish, Sabarinathan, R, Jagadeesan, M, Hemalatha, M S, Rani, D Sudha, Jeyakumar, Annadurai, Sonekar, Harshal Bhimrao, Rubeshkumar, Polani, Prathiksha, G, Bhatnagar, Tarun, Murhekar, Manoj Vasant
• Format: Article
• Language: English
• Subjects: Short Communication
• ISSN: 0035-9203; 1878-3503
• DOI: 10.1093/trstmh/trab136

Background The first serosurvey conducted in Chennai, India in July 2020 reported sudden acute respiratory syndrome coronavirus 2 (SARS-CoV-2) prevalence of 18.4%. The aim of this study was to estimate the seroprevalence in the month of October 2020. Methods We conducted a survey in 153 streets covering 51 wards and all 15 zones of the city and enrolled from each street 40 individuals ≥10 y of age. We collected 3–5 ml of venous blood and tested for anti-nucleocapsid (N) immunoglobulin (IgG) antibodies using a SARS-CoV-2 IgG assay. We estimated the weighted seroprevalence of SARS-CoV-2 infection and adjusted for test characteristics. Results Of the 6366 sera tested, 2052 were positive for anti-N IgG antibodies. The weighted seroprevalence after adjusting for test characteristics was 30.1% (95% confidence interval [CI] 24.7 to 36.1). There was wide variation in the seroprevalence between wards, ranging from 11.0% (95% CI 5.6 to 16.4) to 48.1% (95% CI 39.5 to 56.7). Conclusions The seroprevalence of SARS-CoV-2 infection in Chennai nearly doubled between July and October 2020.