Secondary Attack Rate among the Contacts of COVID-19 Patients at the Beginning of the Pandemic in Pune City of WesternMaharashtra, India

Abstract

Introduction: The COVID-19 was the emerging disease caused by SARS-COV 2. Efficient transmission of this disease occurs through droplets and fomites. As COVID-19 has high transmission and hence susceptible household & non-household close contacts are at high risk of developing disease. Study Objectives: 1) To estimate secondary attack rate of COVID-19 among the contacts during the pandemic in Pune city; 2) To identify factors associated with transmission and development of COVID-19 disease. Material & Methods: This was a retrospective cohort study conducted in the month of June 2020. The sample includes 741 contacts of 119 Laboratory confirmed cases for COVID-19, resides in 15 ward offices areas of Pune Municipal Corporation after written informed consent. A confidential telephonic interview was taken by using a prestructured questionnaire which includes socio demographic data, duration of stay, family background, outcome, type of house, development of symptoms etc. Results: The overall Secondary Attack Rate estimated to be 32.5%, 33.7% among the high risk contacts while 13.3% among the low risk contacts. In this city, 6 wards (40%) out of 15 wards showed SAR of more than 40%. The characteristics of primary cases associated with spread of disease were presence of symptoms and duration between onset of disease and isolation of primary case. The factors significantly affecting SAR were age, comorbidity, no. of family members, type of family, type of house, overcrowding, no. of rooms, bedroom attached with toilet, type of contact & containment zone. Conclusion: Higher SAR was seen in the household contacts. It is necessary to adopt rigorous measures to cut the transmission chain in this area of close contact.