Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection in household contacts and related factors during the firsts waves of the COVID-19 pandemic in Chile: A longitudinal cohort study
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Date
2023
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Universidad de los Andes
Abstract
Background Households are the high-risk setting for SARS-CoV-2 transmission, especially for close and prolonged person-to-person contact. However, the role of household structure and behavioral and clinical factors, especially angiotensin-converting enzyme 2 (ACE2), that contribute to household transmission is scarcely studied. We analyzed the household SARS-CoV-2 infection during the first and second waves of the COVID-19 outbreak and associated factors in household contacts. Method We conducted a prospective cohort study of 109 household clusters with a 60-day follow-up (109 index cases and 248 household contacts) in a selected population in Santiago de Chile. Home interviewers measured: symptoms questionnaire, comorbidities, periodontal condition self-report, compliance with non-pharmaceutical interventions, features of household structure and retrieved saliva samples and nasopharyngeal swabs for ACE2 and SARS-CoV-2 viral load determination. The secondary attack rate (SAR) of SARS-CoV-2 risk factors was assessed using Poisson random-mixed models. Incidence rate ratios (IRR) and p-values are reported. Results The baseline SAR in household contacts was 0.478 (within household variations of 0.03) and 0.023 (0.001) at the end of the follow-up. Of infected households, 13.6% of contacts were asymptomatic at baseline, 23.7% and 12.7% at 7-day and 14-day follow-up, respectively. Infected household contacts were younger (35.9 y vs. 41.1 y, p=0.02), less hypertensive (9.3% vs. 18.5%, p=0.03), and had lower levels of ACE2 (0.04 ng/dl vs. 0.07 ng/dl, p=0.02) than those uninfected. Factors associated with household transmission were a greater number of adult inhabitants (IRR 0.77. p<0.001) and a greater number of rooms (IRR 0.8, p=.003). Conclusion In our study, at the time of index case diagnosis, 47.8% of their household contacts were infected. Meanwhile, at the follow-up only an additional 2.3% were infected. The composition and structure of the home play an essential role in preventing household SARS-CoV-2 transmission. The ACE2 levels may play an important role in household contacts, but further study is needed.