Household transmission of seasonal coronavirus infections: Results from the Flu Watch cohort study

Andrew Hayward; Sarah Beale; Dan Lewer; Robert W. Aldridge; Anne M. Johnson; Maria Zambon; Ellen Fragaszy

doi:10.12688/wellcomeopenres.16055.1

Household transmission of seasonal coronavirus infections: Results from the Flu Watch cohort study

Andrew Hayward^*, Sarah Beale, Dan Lewer, Robert W. Aldridge, Anne M. Johnson, Maria Zambon, Ellen Fragaszy

^*Corresponding author for this work

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Abstract

Background: In the context of the current coronavirus disease 2019 (COVID-19) pandemic, understanding household transmission of seasonal coronaviruses may inform pandemic control. We aimed to investigate what proportion of seasonal coronavirus transmission occurred within households, measure the risk of transmission in households, and describe the impact of household-related factors of risk of transmission.

Methods: Using data from three winter seasons of the UK Flu Watch cohort study, we measured the proportion of symptomatic infections acquired outside and within the home, the household transmission risk and the household secondary attack risk for PCR-confirmed seasonal coronaviruses. We present transmission risk stratified by demographic features of households.

Results: We estimated that the proportion of cases acquired outside the home, weighted by age and region, was 90.7% (95% CI 84.6- 94.5, n=173/195) and within the home was 9.3% (5.5-15.4, 22/195). Following a symptomatic coronavirus index case, 14.9% (9.8 - 22.1, 20/134) of households experienced symptomatic transmission to at least one other household member. Onward transmission risk ranged from 11.90% (4.84-26.36, 5/42) to 19.44% (9.21-36.49, 7/36) by strain. The overall household secondary attack risk for symptomatic cases was 8.00% (5.31-11.88, 22/275), ranging across strains from 5.10 (2.11-11.84, 5/98) to 10.14 (4.82- 20.11, 7/69). Median clinical onset serial interval was 7 days (IQR= 6-9.5). Households including older adults, 3+ children, current smokers, contacts with chronic health conditions, and those in relatively deprived areas had the highest transmission risks. Child index cases and male index cases demonstrated the highest transmission risks.

Conclusion: Most seasonal coronaviruses appear to be acquired outside the household, with relatively modest risk of onward transmission within households. Transmission risk following an index case appears to vary by demographic household features, with potential overlap between those demonstrating the highest point estimates for seasonal coronavirus transmission risk and COVID-19 susceptibility and poor illness outcomes.

Original language	English
Article number	145
Journal	Wellcome Open Research
Volume	5
Early online date	19 Jun 2020
DOIs	https://doi.org/10.12688/wellcomeopenres.16055.1
Publication status	Published - 21 Jun 2021

Bibliographical note

Funding Information: This project was supported by the Wellcome Trust through funding to the Flu Watch Study [091011]. The Flu Watch study received funding from the Medical Research Council (MRC) and the Wellcome Trust [091011, G0600511, G0800767 and MC_U122785833]. SB is supported by an MRC doctoral studentship [MR/N013867/1]. The funders were not actively involved in the design, delivery, or analysis of this research. The views expressed in this publication are those of the authors and not necessarily of the MRC or the Wellcome Trust. AH is an NIHR Senior Investigator. The views expressed in this Article are those of the authors and not necessarily those of the NIHR, or the Department of Health and Social Care. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
AH serves on the UK New and Emerging Respiratory Virus Threats Advisory Group. AMJ was a Governor of Wellcome Trust from 2011-18 and is Chair of the Committee for Strategic Coordination for Health of the Public Research. The other
authors declare no competing interests.

Open Access: This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Publisher Copyright: © 2020 Beale S et al.

Citation: Beale S, Lewer D, Aldridge RW et al. Household transmission of seasonal coronavirus infections: Results from the Flu Watch cohort study [version 1; peer review: 1 approved, 2 approved with reservations] Wellcome Open Research 2020, 5:145

DOI: https://doi.org/10.12688/wellcomeopenres.16055.1

Keywords

Coronavirus
Epidemiology
HCoV-229E
HCoV-NL63
HCoV-OC43
SARS-CoV-2

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Cite this

@article{e176bb2951ec4cb5b67135a828008d04,

title = "Household transmission of seasonal coronavirus infections: Results from the Flu Watch cohort study",

abstract = "Background: In the context of the current coronavirus disease 2019 (COVID-19) pandemic, understanding household transmission of seasonal coronaviruses may inform pandemic control. We aimed to investigate what proportion of seasonal coronavirus transmission occurred within households, measure the risk of transmission in households, and describe the impact of household-related factors of risk of transmission. Methods: Using data from three winter seasons of the UK Flu Watch cohort study, we measured the proportion of symptomatic infections acquired outside and within the home, the household transmission risk and the household secondary attack risk for PCR-confirmed seasonal coronaviruses. We present transmission risk stratified by demographic features of households. Results: We estimated that the proportion of cases acquired outside the home, weighted by age and region, was 90.7\% (95\% CI 84.6- 94.5, n=173/195) and within the home was 9.3\% (5.5-15.4, 22/195). Following a symptomatic coronavirus index case, 14.9\% (9.8 - 22.1, 20/134) of households experienced symptomatic transmission to at least one other household member. Onward transmission risk ranged from 11.90\% (4.84-26.36, 5/42) to 19.44\% (9.21-36.49, 7/36) by strain. The overall household secondary attack risk for symptomatic cases was 8.00\% (5.31-11.88, 22/275), ranging across strains from 5.10 (2.11-11.84, 5/98) to 10.14 (4.82- 20.11, 7/69). Median clinical onset serial interval was 7 days (IQR= 6-9.5). Households including older adults, 3+ children, current smokers, contacts with chronic health conditions, and those in relatively deprived areas had the highest transmission risks. Child index cases and male index cases demonstrated the highest transmission risks. Conclusion: Most seasonal coronaviruses appear to be acquired outside the household, with relatively modest risk of onward transmission within households. Transmission risk following an index case appears to vary by demographic household features, with potential overlap between those demonstrating the highest point estimates for seasonal coronavirus transmission risk and COVID-19 susceptibility and poor illness outcomes.",

keywords = "Coronavirus, Epidemiology, HCoV-229E, HCoV-NL63, HCoV-OC43, SARS-CoV-2",

author = "Andrew Hayward and Sarah Beale and Dan Lewer and Aldridge, \{Robert W.\} and Johnson, \{Anne M.\} and Maria Zambon and Ellen Fragaszy",

note = "Funding Information: This project was supported by the Wellcome Trust through funding to the Flu Watch Study [091011]. The Flu Watch study received funding from the Medical Research Council (MRC) and the Wellcome Trust [091011, G0600511, G0800767 and MC\_U122785833]. SB is supported by an MRC doctoral studentship [MR/N013867/1]. The funders were not actively involved in the design, delivery, or analysis of this research. The views expressed in this publication are those of the authors and not necessarily of the MRC or the Wellcome Trust. AH is an NIHR Senior Investigator. The views expressed in this Article are those of the authors and not necessarily those of the NIHR, or the Department of Health and Social Care. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript AH serves on the UK New and Emerging Respiratory Virus Threats Advisory Group. AMJ was a Governor of Wellcome Trust from 2011-18 and is Chair of the Committee for Strategic Coordination for Health of the Public Research. The other authors declare no competing interests. Open Access: This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Publisher Copyright: {\textcopyright} 2020 Beale S et al. Citation: Beale S, Lewer D, Aldridge RW et al. Household transmission of seasonal coronavirus infections: Results from the Flu Watch cohort study [version 1; peer review: 1 approved, 2 approved with reservations] Wellcome Open Research 2020, 5:145 DOI: https://doi.org/10.12688/wellcomeopenres.16055.1",

year = "2021",

month = jun,

day = "21",

doi = "10.12688/wellcomeopenres.16055.1",

language = "English",

volume = "5",

journal = "Wellcome Open Research",

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TY - JOUR

T1 - Household transmission of seasonal coronavirus infections

T2 - Results from the Flu Watch cohort study

AU - Hayward, Andrew

AU - Beale, Sarah

AU - Lewer, Dan

AU - Aldridge, Robert W.

AU - Johnson, Anne M.

AU - Zambon, Maria

AU - Fragaszy, Ellen

N1 - Funding Information: This project was supported by the Wellcome Trust through funding to the Flu Watch Study [091011]. The Flu Watch study received funding from the Medical Research Council (MRC) and the Wellcome Trust [091011, G0600511, G0800767 and MC_U122785833]. SB is supported by an MRC doctoral studentship [MR/N013867/1]. The funders were not actively involved in the design, delivery, or analysis of this research. The views expressed in this publication are those of the authors and not necessarily of the MRC or the Wellcome Trust. AH is an NIHR Senior Investigator. The views expressed in this Article are those of the authors and not necessarily those of the NIHR, or the Department of Health and Social Care. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript AH serves on the UK New and Emerging Respiratory Virus Threats Advisory Group. AMJ was a Governor of Wellcome Trust from 2011-18 and is Chair of the Committee for Strategic Coordination for Health of the Public Research. The other authors declare no competing interests. Open Access: This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Publisher Copyright: © 2020 Beale S et al. Citation: Beale S, Lewer D, Aldridge RW et al. Household transmission of seasonal coronavirus infections: Results from the Flu Watch cohort study [version 1; peer review: 1 approved, 2 approved with reservations] Wellcome Open Research 2020, 5:145 DOI: https://doi.org/10.12688/wellcomeopenres.16055.1

PY - 2021/6/21

Y1 - 2021/6/21

N2 - Background: In the context of the current coronavirus disease 2019 (COVID-19) pandemic, understanding household transmission of seasonal coronaviruses may inform pandemic control. We aimed to investigate what proportion of seasonal coronavirus transmission occurred within households, measure the risk of transmission in households, and describe the impact of household-related factors of risk of transmission. Methods: Using data from three winter seasons of the UK Flu Watch cohort study, we measured the proportion of symptomatic infections acquired outside and within the home, the household transmission risk and the household secondary attack risk for PCR-confirmed seasonal coronaviruses. We present transmission risk stratified by demographic features of households. Results: We estimated that the proportion of cases acquired outside the home, weighted by age and region, was 90.7% (95% CI 84.6- 94.5, n=173/195) and within the home was 9.3% (5.5-15.4, 22/195). Following a symptomatic coronavirus index case, 14.9% (9.8 - 22.1, 20/134) of households experienced symptomatic transmission to at least one other household member. Onward transmission risk ranged from 11.90% (4.84-26.36, 5/42) to 19.44% (9.21-36.49, 7/36) by strain. The overall household secondary attack risk for symptomatic cases was 8.00% (5.31-11.88, 22/275), ranging across strains from 5.10 (2.11-11.84, 5/98) to 10.14 (4.82- 20.11, 7/69). Median clinical onset serial interval was 7 days (IQR= 6-9.5). Households including older adults, 3+ children, current smokers, contacts with chronic health conditions, and those in relatively deprived areas had the highest transmission risks. Child index cases and male index cases demonstrated the highest transmission risks. Conclusion: Most seasonal coronaviruses appear to be acquired outside the household, with relatively modest risk of onward transmission within households. Transmission risk following an index case appears to vary by demographic household features, with potential overlap between those demonstrating the highest point estimates for seasonal coronavirus transmission risk and COVID-19 susceptibility and poor illness outcomes.

AB - Background: In the context of the current coronavirus disease 2019 (COVID-19) pandemic, understanding household transmission of seasonal coronaviruses may inform pandemic control. We aimed to investigate what proportion of seasonal coronavirus transmission occurred within households, measure the risk of transmission in households, and describe the impact of household-related factors of risk of transmission. Methods: Using data from three winter seasons of the UK Flu Watch cohort study, we measured the proportion of symptomatic infections acquired outside and within the home, the household transmission risk and the household secondary attack risk for PCR-confirmed seasonal coronaviruses. We present transmission risk stratified by demographic features of households. Results: We estimated that the proportion of cases acquired outside the home, weighted by age and region, was 90.7% (95% CI 84.6- 94.5, n=173/195) and within the home was 9.3% (5.5-15.4, 22/195). Following a symptomatic coronavirus index case, 14.9% (9.8 - 22.1, 20/134) of households experienced symptomatic transmission to at least one other household member. Onward transmission risk ranged from 11.90% (4.84-26.36, 5/42) to 19.44% (9.21-36.49, 7/36) by strain. The overall household secondary attack risk for symptomatic cases was 8.00% (5.31-11.88, 22/275), ranging across strains from 5.10 (2.11-11.84, 5/98) to 10.14 (4.82- 20.11, 7/69). Median clinical onset serial interval was 7 days (IQR= 6-9.5). Households including older adults, 3+ children, current smokers, contacts with chronic health conditions, and those in relatively deprived areas had the highest transmission risks. Child index cases and male index cases demonstrated the highest transmission risks. Conclusion: Most seasonal coronaviruses appear to be acquired outside the household, with relatively modest risk of onward transmission within households. Transmission risk following an index case appears to vary by demographic household features, with potential overlap between those demonstrating the highest point estimates for seasonal coronavirus transmission risk and COVID-19 susceptibility and poor illness outcomes.

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KW - Epidemiology

KW - HCoV-229E

KW - HCoV-NL63

KW - HCoV-OC43

KW - SARS-CoV-2

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SN - 2398-502X

VL - 5

JO - Wellcome Open Research

JF - Wellcome Open Research

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ER -

Household transmission of seasonal coronavirus infections: Results from the Flu Watch cohort study

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