Social contact patterns and implications for infectious disease transmission: a systematic review and meta-analysis of contact surveys
Abstract
Background: Transmission of respiratory pathogens such as SARS-CoV-2 depends on patterns of contact and mixing across populations. Understanding this is crucial to predict pathogen spread and the effectiveness of control efforts. Most analyses of contact patterns to date have focussed on high-income settings.
Methods: Here, we conduct a systematic review and individual-participant meta-analysis of surveys carried out in low- and middle-income countries and compare patterns of contact in these settings to surveys previously carried out in high-income countries. Using individual-level data from 28,503 participants and 413,069 contacts across 27 surveys we explored how contact characteristics (number, location, duration and whether physical) vary across income settings.
Results: Contact rates declined with age in high- and upper-middle-income settings, but not in low-income settings, where adults aged 65+ made similar numbers of contacts as younger individuals and mixed with all age-groups. Across all settings, increasing household size was a key determinant of contact frequency and characteristics, with low-income settings characterised by the largest, most intergenerational households. A higher proportion of contacts were made at home in low-income settings, and work/school contacts were more frequent in high-income strata. We also observed contrasting effects of gender across income-strata on the frequency, duration and type of contacts individuals made.
Conclusions: These differences in contact patterns between settings have material consequences for both spread of respiratory pathogens, as well as the effectiveness of different non-pharmaceutical interventions.
Funding: This work is primarily being funded by joint Centre funding from the UK Medical Research Council and DFID (MR/R015600/1).
Data availability
All individual-level data across all studies and analysis code are available at https://github.com/mrc-ide/contact_patterns (see Supplementary Text 4 for data dictionary).
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Article and author information
Author details
Funding
joint Centre funding from the UK Medical Research Council and DFID (MR/R015600/1)
- Andria Mousa
- Peter Winskill
- Patrick Walker
- Charles Whittaker
Australian National Health and Medical Research Council
- Fiona M Russell
WHO
- Fiona M Russell
Bill & Melinda Gates Foundation
- Fiona M Russell
Wellcome Trust
- Fiona M Russell
DFAT
- Fiona M Russell
EPSRC through the EPSRC Centre for Doctoral Training in Modern Statistics and Statistical Machine Learning
- Mélodie Monod
University of Washington
- Jonathan D Sugimoto
US National Institutes of Health, NIAID
- Jonathan D Sugimoto
NIH (K24AI148459)
- Carlos G Grijalva
General Medical Sciences / National Institute of Health (U01-GM070749)
- Gail E Potter
UK foreign Commonwealth and Development Office
- Oliver John Watson
Emmes Company
- Gail E Potter
CUHK Direct grant for research (2019.020)
- Kin O Kwok
Health and Medical Research Fund (INF-CUHK-1,17160302,18170312)
- Kin O Kwok
General Research Fund (14112818)
- Kin O Kwok
Early Career Scheme (24104920)
- Kin O Kwok
Wellcome Trust (200861/Z/16/Z)
- Kin O Kwok
UK Medical Research Council. UK-funded award is part of the EDCTP2 programme supported by the EU (MR/P022081/1)
- Peter J Dodd
Australian Government Research Training Program Scholarship
- Eleanor FG Neal
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Reviewing Editor
- Isabel Rodriguez-Barraquer, University of California, San Francisco, United States
Ethics
Human subjects: All original studies included were approved by an institutional ethics review committee. Ethics approval was not required for the present study.
Version history
- Received: May 12, 2021
- Accepted: November 24, 2021
- Accepted Manuscript published: November 25, 2021 (version 1)
- Version of Record published: January 18, 2022 (version 2)
Copyright
This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.
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Further reading
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- Epidemiology and Global Health
Background:
The aim of our study was to test the hypothesis that the community contact tracing strategy of testing contacts in households immediately instead of at the end of quarantine had an impact on the transmission of SARS-CoV-2 in schools in Reggio Emilia Province.
Methods:
We analysed surveillance data on notification of COVID-19 cases in schools between 1 September 2020 and 4 April 2021. We have applied a mediation analysis that allows for interaction between the intervention (before/after period) and the mediator.
Results:
Median tracing delay decreased from 7 to 3.1 days and the percentage of the known infection source increased from 34–54.8% (incident rate ratio-IRR 1.61 1.40–1.86). Implementation of prompt contact tracing was associated with a 10% decrease in the number of secondary cases (excess relative risk –0.1 95% CI –0.35–0.15). Knowing the source of infection of the index case led to a decrease in secondary transmission (IRR 0.75 95% CI 0.63–0.91) while the decrease in tracing delay was associated with decreased risk of secondary cases (1/IRR 0.97 95% CI 0.94–1.01 per one day of delay). The direct effect of the intervention accounted for the 29% decrease in the number of secondary cases (excess relative risk –0.29 95%–0.61 to 0.03).
Conclusions:
Prompt contact testing in the community reduces the time of contact tracing and increases the ability to identify the source of infection in school outbreaks. Although there are strong reasons for thinking it is a causal link, observed differences can be also due to differences in the force of infection and to other control measures put in place.
Funding:
This project was carried out with the technical and financial support of the Italian Ministry of Health – CCM 2020 and Ricerca Corrente Annual Program 2023.
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- Epidemiology and Global Health
In biomedical science, it is a reality that many published results do not withstand deeper investigation, and there is growing concern over a replicability crisis in science. Recently, Ellipse of Insignificance (EOI) analysis was introduced as a tool to allow researchers to gauge the robustness of reported results in dichotomous outcome design trials, giving precise deterministic values for the degree of miscoding between events and non-events tolerable simultaneously in both control and experimental arms (Grimes, 2022). While this is useful for situations where potential miscoding might transpire, it does not account for situations where apparently significant findings might result from accidental or deliberate data redaction in either the control or experimental arms of an experiment, or from missing data or systematic redaction. To address these scenarios, we introduce Region of Attainable Redaction (ROAR), a tool that extends EOI analysis to account for situations of potential data redaction. This produces a bounded cubic curve rather than an ellipse, and we outline how this can be used to identify potential redaction through an approach analogous to EOI. Applications are illustrated, and source code, including a web-based implementation that performs EOI and ROAR analysis in tandem for dichotomous outcome trials is provided.