A preliminary study on contact tracing & transmission chain in a cluster of 17 cases of severe acute respiratory syndrome coronavirus 2 infection in Basti, Uttar Pradesh, India

Abstract

Background & objectives: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has spread rapidly, causing unprecedented case fatalities across the world. The first laboratory-confirmed case of COVID-19 and also the first death associated with the disease in the eastern part of Uttar Pradesh (UP) was reported from Basti on March 31, 2020. The present study describes a cluster of 17 cases including one death of confirmed COVID-19 in Basti, UP, India. Methods: A 25 year old male from Basti, UP, India, who died of respiratory failure was diagnosed post-mortem as SARS-CoV-2 positive. Contact tracing carried out by the district administration found 16 cases positive among tested contacts. A detailed retrospective investigation in the form of one-to-one interview was carried out with 16 recovered individuals to understand the transmission dynamics and clinical characteristics. Results: The findings showed that the cluster transmission occurred at three levels: first was direct contact with the index case which resulted in two secondary cases. Second, at a household level where four of the seven susceptible contacts got infected, and the third was an event (funeral) where 50 individuals participated and this resulted in seven SARS-CoV-2-infected individuals in whom infection could be directly linked to a funeral gathering. The index case had associated comorbidities and succumbed to death. Most of the cases were asymptomatic except two individuals, who developed mild symptoms. The mean duration of quarantine facility was 21.6±7.3 days, and the average time taken for the first negative test after testing positive to COVID-19 was 12±4.1 days. Interpretation & conclusions: The funeral acted as a super-spreader event for the transmission of infection among family members, relatives and others. Active contact tracing and confirmation of infection among the contacts led to the isolation of 16 SARS-CoV-2 positive cases and hence the limited spread of the disease. Asymptomatic carriers and super-spreader events are among the major challenges in the control and prevention of SARS-CoV-2 transmission. Early testing, quarantine and social distancing may play key role in breaking the chain of transmission. 2020 Indian Journal of Medical Research, published by Wolters Kluwer - Medknow for Director-General, Indian Council of Medical Research.