Seroprevalence of SARS-CoV-2 specific IgG antibodies in District Srinagar, northern India – a cross-sectional study

Salim Khan, S Muhammad; Qurieshi, Mariya Amin; Haq, Inaamul; Majid, Sabhiya; Bhat, Arif Akbar; Nabi, Sahila; Ganai, Nisar Ahmad; Zahoor, Nazia; Nisar, Auqfeen; Chowdri, Iqra Nisar; Qazi, Tanzeela Bashir; Kousar, Rafiya; Lone, Abdul Aziz; Sabah, Iram; Nabi, Shahroz; Sumji, Ishtiyaq Ahmad; Kawoosa, Misbah Ferooz; Ayoub, Shifana

Background Prevalence of IgG antibodies against SARS-CoV-2 infection provides essential information for deciding disease prevention and mitigation measures. We estimate the seroprevalence of SARS-CoV-2 specific IgG antibodies in District Srinagar. Methods 2906 persons >18 years of age selected from hospital visitors across District Srinagar participated in the study. We tested samples for the presence of SARS-CoV-2 specific IgG antibodies using a chemiluminescent microparticle immunoassay-based serologic test. Results Age- and gender-standardized seroprevalence was 3.6% (95% CI 2.9% to 4.3%). Age 30-69 years, a recent history of symptoms of an influenza-like-illness, and a history of being placed under quarantine were significantly related to higher odds of the presence of SARS-CoV-2 specific IgG antibodies. The estimated number of SARS-CoV-2 infections during the two weeks preceding the study, adjusted for test performance, was 32602 with an estimated (median) infection-to-known-case ratio of 46 (95% CI 36 to 57). Conclusions The seroprevalence of SARS-CoV-2 specific IgG antibodies is low in the District. A large proportion of the population is still susceptible to the infection. A sizeable number of infections remain undetected, and a substantial proportion of people with symptoms compatible with COVID-19 are not tested.