SARS-CoV-2 infection and seropositivity among household contacts of laboratory confirmed cases of COVID-19 in residents of Delhi, India

• Published in: Preventive medicine reports Vol. 38; p. 102603
• Main Authors: Das, Ayan Kumar, Islam, Farzana, Alvi, Yasir, Dudeja, Mridu, Ahmad, Mohammad, Rahman, Anisur, Roy, Sushovan, Aamir, Ahmed, Maroof
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.02.2024; Elsevier
• Subjects: Asymptomatic infection; Household transmission; Regular article; RT-PCR; SARS-CoV-2; Secondary infection rate; Seroconversion; Asymptomatic infection; SARS-CoV-2; Secondary infection rate; Seroconversion; RT-PCR; Household transmission
• ISSN: 2211-3355; 2211-3355
• DOI: 10.1016/j.pmedr.2024.102603

The transmission of respiratory pathogens, including SARS-CoV-2, is often facilitated through household contact. To better understand the transmission rate of COVID-19 among households and factors that affect viral clearance and seroconversion, a case-ascertained community-based prospective study was conducted between December 2020 and June 2021 on the urban population of the national capital region of India. The study collected nasopharyngeal swabs for SARS-CoV-2 RT-PCR on the 1st, 7th, 14th, and 28th day, and blood samples for antibody detection on the 1st, 14th, and 28th day from household contacts (HCs) of laboratory-confirmed COVID-19 cases. The study monitored the demographic data, symptoms, and outcomes of 417 participants, including 99 index cases and 318 contacts, for a period of 28 days. The results of the study showed that SARS-CoV-2 was easily spread within households, with a secondary infection rate of 44.3 %. In fact, almost 70 % of the contacts got infected within 1–2 days of identification of the index case, while 34 % remained asymptomatic. Sero-conversion was found in 35.6 % of the participants while 22.9 % did not produce antibodies after 28 days of infection. The study also revealed that females, spouses, older members, and primary care providers were at higher risk of getting infected in a home setting. However, approximately one-third of individuals in the younger age group managed to avoid infection. The study demonstrated that most infected individuals became RT-PCR negative within two weeks, although viral clearance was delayed in older patients and those with lower cycle threshold values in RT-PCR.