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Household transmission of SARS-CoV-2 and risk factors for susceptibility and infectivity in Wuhan: a retrospective observational study.
Lancet Infect Dis. 2021 05; 21(5):617-628.LI

Abstract

BACKGROUND

Wuhan was the first epicentre of COVID-19 in the world, accounting for 80% of cases in China during the first wave. We aimed to assess household transmissibility of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and risk factors associated with infectivity and susceptibility to infection in Wuhan.

METHODS

This retrospective cohort study included the households of all laboratory-confirmed or clinically confirmed COVID-19 cases and laboratory-confirmed asymptomatic SARS-CoV-2 infections identified by the Wuhan Center for Disease Control and Prevention between Dec 2, 2019, and April 18, 2020. We defined households as groups of family members and close relatives who did not necessarily live at the same address and considered households that shared common contacts as epidemiologically linked. We used a statistical transmission model to estimate household secondary attack rates and to quantify risk factors associated with infectivity and susceptibility to infection, accounting for individual-level exposure history. We assessed how intervention policies affected the household reproductive number, defined as the mean number of household contacts a case can infect.

FINDINGS

27 101 households with 29 578 primary cases and 57 581 household contacts were identified. The secondary attack rate estimated with the transmission model was 15·6% (95% CI 15·2-16·0), assuming a mean incubation period of 5 days and a maximum infectious period of 22 days. Individuals aged 60 years or older were at a higher risk of infection with SARS-CoV-2 than all other age groups. Infants aged 0-1 years were significantly more likely to be infected than children aged 2-5 years (odds ratio [OR] 2·20, 95% CI 1·40-3·44) and children aged 6-12 years (1·53, 1·01-2·34). Given the same exposure time, children and adolescents younger than 20 years of age were more likely to infect others than were adults aged 60 years or older (1·58, 1·28-1·95). Asymptomatic individuals were much less likely to infect others than were symptomatic cases (0·21, 0·14-0·31). Symptomatic cases were more likely to infect others before symptom onset than after (1·42, 1·30-1·55). After mass isolation of cases, quarantine of household contacts, and restriction of movement policies were implemented, household reproductive numbers declined by 52% among primary cases (from 0·25 [95% CI 0·24-0·26] to 0·12 [0·10-0·13]) and by 63% among secondary cases (from 0·17 [0·16-0·18] to 0·063 [0·057-0·070]).

INTERPRETATION

Within households, children and adolescents were less susceptible to SARS-CoV-2 infection but were more infectious than older individuals. Presymptomatic cases were more infectious and individuals with asymptomatic infection less infectious than symptomatic cases. These findings have implications for devising interventions for blocking household transmission of SARS-CoV-2, such as timely vaccination of eligible children once resources become available.

FUNDING

National Natural Science Foundation of China, Fundamental Research Funds for the Central Universities, US National Institutes of Health, and US National Science Foundation.

Authors+Show Affiliations

Wuhan Center for Disease Control and Prevention, Wuhan, Hubei, China.School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.Department of Biostatistics, College of Public Health and Health Professions & Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA.State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China.Department of Biostatistics, College of Public Health and Health Professions & Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA.Department of Pediatrics, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong Special Administrative Region, China.Wuhan Center for Disease Control and Prevention, Wuhan, Hubei, China.Department of Biostatistics, College of Public Health and Health Professions & Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA.Vaccine and Infectious Diseases Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA; Department of Biostatistics, University of Washington, Seattle, WA, USA.Wuhan Center for Disease Control and Prevention, Wuhan, Hubei, China.Wuhan Center for Disease Control and Prevention, Wuhan, Hubei, China.Wuhan Center for Disease Control and Prevention, Wuhan, Hubei, China.Wuhan Center for Disease Control and Prevention, Wuhan, Hubei, China.Wuhan Center for Disease Control and Prevention, Wuhan, Hubei, China.School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.Department of Respiratory Medicine, Wuhan Children's Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.Department of Biostatistics, College of Public Health and Health Professions & Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA. Electronic address: yangyang@ufl.edu.School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China. Electronic address: xust@hust.edu.cn.

Pub Type(s)

Journal Article
Observational Study
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

33476567

Citation

Li, Fang, et al. "Household Transmission of SARS-CoV-2 and Risk Factors for Susceptibility and Infectivity in Wuhan: a Retrospective Observational Study." The Lancet. Infectious Diseases, vol. 21, no. 5, 2021, pp. 617-628.
Li F, Li YY, Liu MJ, et al. Household transmission of SARS-CoV-2 and risk factors for susceptibility and infectivity in Wuhan: a retrospective observational study. Lancet Infect Dis. 2021;21(5):617-628.
Li, F., Li, Y. Y., Liu, M. J., Fang, L. Q., Dean, N. E., Wong, G. W. K., Yang, X. B., Longini, I., Halloran, M. E., Wang, H. J., Liu, P. L., Pang, Y. H., Yan, Y. Q., Liu, S., Xia, W., Lu, X. X., Liu, Q., Yang, Y., & Xu, S. Q. (2021). Household transmission of SARS-CoV-2 and risk factors for susceptibility and infectivity in Wuhan: a retrospective observational study. The Lancet. Infectious Diseases, 21(5), 617-628. https://doi.org/10.1016/S1473-3099(20)30981-6
Li F, et al. Household Transmission of SARS-CoV-2 and Risk Factors for Susceptibility and Infectivity in Wuhan: a Retrospective Observational Study. Lancet Infect Dis. 2021;21(5):617-628. PubMed PMID: 33476567.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Household transmission of SARS-CoV-2 and risk factors for susceptibility and infectivity in Wuhan: a retrospective observational study. AU - Li,Fang, AU - Li,Yuan-Yuan, AU - Liu,Ming-Jin, AU - Fang,Li-Qun, AU - Dean,Natalie E, AU - Wong,Gary W K, AU - Yang,Xiao-Bing, AU - Longini,Ira, AU - Halloran,M Elizabeth, AU - Wang,Huai-Ji, AU - Liu,Pu-Lin, AU - Pang,Yan-Hui, AU - Yan,Ya-Qiong, AU - Liu,Su, AU - Xia,Wei, AU - Lu,Xiao-Xia, AU - Liu,Qi, AU - Yang,Yang, AU - Xu,Shun-Qing, Y1 - 2021/01/18/ PY - 2020/09/18/received PY - 2020/11/08/revised PY - 2020/12/07/accepted PY - 2021/1/22/pubmed PY - 2021/5/4/medline PY - 2021/1/21/entrez SP - 617 EP - 628 JF - The Lancet. Infectious diseases JO - Lancet Infect Dis VL - 21 IS - 5 N2 - BACKGROUND: Wuhan was the first epicentre of COVID-19 in the world, accounting for 80% of cases in China during the first wave. We aimed to assess household transmissibility of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and risk factors associated with infectivity and susceptibility to infection in Wuhan. METHODS: This retrospective cohort study included the households of all laboratory-confirmed or clinically confirmed COVID-19 cases and laboratory-confirmed asymptomatic SARS-CoV-2 infections identified by the Wuhan Center for Disease Control and Prevention between Dec 2, 2019, and April 18, 2020. We defined households as groups of family members and close relatives who did not necessarily live at the same address and considered households that shared common contacts as epidemiologically linked. We used a statistical transmission model to estimate household secondary attack rates and to quantify risk factors associated with infectivity and susceptibility to infection, accounting for individual-level exposure history. We assessed how intervention policies affected the household reproductive number, defined as the mean number of household contacts a case can infect. FINDINGS: 27 101 households with 29 578 primary cases and 57 581 household contacts were identified. The secondary attack rate estimated with the transmission model was 15·6% (95% CI 15·2-16·0), assuming a mean incubation period of 5 days and a maximum infectious period of 22 days. Individuals aged 60 years or older were at a higher risk of infection with SARS-CoV-2 than all other age groups. Infants aged 0-1 years were significantly more likely to be infected than children aged 2-5 years (odds ratio [OR] 2·20, 95% CI 1·40-3·44) and children aged 6-12 years (1·53, 1·01-2·34). Given the same exposure time, children and adolescents younger than 20 years of age were more likely to infect others than were adults aged 60 years or older (1·58, 1·28-1·95). Asymptomatic individuals were much less likely to infect others than were symptomatic cases (0·21, 0·14-0·31). Symptomatic cases were more likely to infect others before symptom onset than after (1·42, 1·30-1·55). After mass isolation of cases, quarantine of household contacts, and restriction of movement policies were implemented, household reproductive numbers declined by 52% among primary cases (from 0·25 [95% CI 0·24-0·26] to 0·12 [0·10-0·13]) and by 63% among secondary cases (from 0·17 [0·16-0·18] to 0·063 [0·057-0·070]). INTERPRETATION: Within households, children and adolescents were less susceptible to SARS-CoV-2 infection but were more infectious than older individuals. Presymptomatic cases were more infectious and individuals with asymptomatic infection less infectious than symptomatic cases. These findings have implications for devising interventions for blocking household transmission of SARS-CoV-2, such as timely vaccination of eligible children once resources become available. FUNDING: National Natural Science Foundation of China, Fundamental Research Funds for the Central Universities, US National Institutes of Health, and US National Science Foundation. SN - 1474-4457 UR - https://www.unboundmedicine.com/medline/citation/33476567/Household_transmission_of_SARS_CoV_2_and_risk_factors_for_susceptibility_and_infectivity_in_Wuhan:_a_retrospective_observational_study_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S1473-3099(20)30981-6 DB - PRIME DP - Unbound Medicine ER -