Prevalence of SARS-CoV-2 infection in India
Authors: Murhekar Manoj V. , Bhatnagar Tarun , Selvaraju Sriram , Rade Kiran , Saravanakumar V. , Vivian Thangaraj Jeromie Wesley , Kumar Muthusamy Santhosh , Shah Naman , Sabarinathan R. , Turuk Alka , Anand Parveen Kumar , Asthana Smita , Balachandar Rakesh , Bangar Sampada Dipak , Bansal Avi Kumar , Bhat Jyothi , Chakraborty Debjit , Rangaraju Chethana , Chopra Vishal , Das Dasarathi , Deb Alok Kumar , Devi Kangjam Rekha , Dwivedi Gaurav Raj , Salim Khan S. Muhammad , Haq Inaamul , Kumar M. Sunil , Laxmaiah Avula , (Major) Madhukar  , Mahapatra Amarendra , Mitra Anindya , Nirmala A.R. , Pagdhune Avinash , Qurieshi Mariya Amin , Ramarao Tekumalla , Sahay Seema , Sharma Y.K. , Shrinivasa Marinaik Basavegowdanadoddi , Shukla Vijay Kumar , Singh Prashant Kumar , Viramgami Ankit , Wilson Vimith Cheruvathoor , Yadav Rajiv , Girish Kumar C.P. , Luke Hanna Elizabeth , Ranganathan Uma Devi , Babu Subash , Sekar Krithikaa , Yadav Pragya D. , Sapkal Gajanan N. , Das Aparup , Das Pradeep , Dutta Shanta , Hemalatha Rajkumar , Kumar Ashwani , Narain Kanwar , Narasimhaiah Somashekar , Panda Samiran , Pati Sanghamitra , Patil Shripad , Sarkar Kamalesh , Singh Shalini , Kant Rajni , Tripathy Srikanth , Toteja G.S. , Babu Giridhara R. , Kant Shashi , Muliyil J.P. , Pandey Ravindra Mohan , Sarkar Swarup , Singh Sujeet K. , Zodpey Sanjay , Gangakhedkar Raman R. , Reddy D.C.S. , Bhargava Balram 
Published: September 2020

Background & objectives:
Population-based seroepidemiological studies measure the extent of SARS-CoV-2 infection in a country. We report the findings of the first round of a national serosurvey, conducted to estimate the seroprevalence of SARS-CoV-2 infection among adult population of India.

Methods:
From May 11 to June 4, 2020, a randomly sampled, community-based survey was conducted in 700 villages/wards, selected from the 70 districts of the 21 States of India, categorized into four strata based on the incidence of reported COVID-19 cases. Four hundred adults per district were enrolled from 10 clusters with one adult per household. Serum samples were tested for IgG antibodies using COVID Kavach ELISA kit. All positive serum samples were re-tested using Euroimmun SARS-CoV-2 ELISA. Adjusting for survey design and serial test performance, weighted seroprevalence, number of infections, infection to case ratio (ICR) and infection fatality ratio (IFR) were calculated. Logistic regression was used to determine the factors associated with IgG positivity.

Results:
Total of 30,283 households were visited and 28,000 individuals were enrolled. Population-weighted seroprevalence after adjusting for test performance was 0.73 per cent [95% confidence interval (CI): 0.34-1.13]. Males, living in urban slums and occupation with high risk of exposure to potentially infected persons were associated with seropositivity. A cumulative 6,468,388 adult infections (95% CI: 3,829,029-11,199,423) were estimated in India by the early May. The overall ICR was between 81.6 (95% CI: 48.3-141.4) and 130.1 (95% CI: 77.0-225.2) with May 11 and May 3, 2020 as plausible reference points for reported cases. The IFR in the surveyed districts from high stratum, where death reporting was more robust, was 11.72 (95% CI: 7.21-19.19) to 15.04 (9.26-24.62) per 10,000 adults, using May 24 and June 1, 2020 as plausible reference points for reported deaths.

Interpretation & conclusions:
Seroprevalence of SARS-CoV-2 was low among the adult population in India around the beginning of May 2020. Further national and local serosurveys are recommended to better inform the public health strategy for containment and mitigation of the epidemic in various parts of the country.