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McAloon CG, Wall P, Butler F, Codd M, Gormley E, Walsh C, Duggan J, Murphy TB, Nolan P, Smyth B, O'Brien K, Teljeur C, Green MJ, O'Grady L, Culhane K, Buckley C, Carroll C, Doyle S, Martin J, More SJ. Numbers of close contacts of individuals infected with SARS-CoV-2 and their association with government intervention strategies. BMC Public Health 2021; 21:2238. [PMID: 34886842 PMCID: PMC8655330 DOI: 10.1186/s12889-021-12318-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 11/22/2021] [Indexed: 12/23/2022] Open
Abstract
Background Contact tracing is conducted with the primary purpose of interrupting transmission from individuals who are likely to be infectious to others. Secondary analyses of data on the numbers of close contacts of confirmed cases could also: provide an early signal of increases in contact patterns that might precede larger than expected case numbers; evaluate the impact of government interventions on the number of contacts of confirmed cases; or provide data information on contact rates between age cohorts for the purpose of epidemiological modelling. We analysed data from 140,204 close contacts of 39,861 cases in Ireland from 1st May to 1st December 2020. Results Negative binomial regression models highlighted greater numbers of contacts within specific population demographics, after correcting for temporal associations. Separate segmented regression models of the number of cases over time and the average number of contacts per case indicated that a breakpoint indicating a rapid decrease in the number of contacts per case in October 2020 preceded a breakpoint indicating a reduction in the number of cases by 11 days. Conclusions We found that the number of contacts per infected case was overdispersed, the mean varied considerable over time and was temporally associated with government interventions. Analysis of the reported number of contacts per individual in contact tracing data may be a useful early indicator of changes in behaviour in response to, or indeed despite, government restrictions. This study provides useful information for triangulating assumptions regarding the contact mixing rates between different age cohorts for epidemiological modelling. Supplementary Information The online version contains supplementary material available at 10.1186/s12889-021-12318-y.
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Affiliation(s)
- Conor G McAloon
- School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
| | - Patrick Wall
- School of Public Health, Physiotherapy and Sports Science, University College Dublin, Belfield, Dublin 4, Ireland
| | - Francis Butler
- School of Biosystems and Food Engineering, University College Dublin, Belfield, Dublin 4, Ireland
| | - Mary Codd
- School of Public Health, Physiotherapy and Sports Science, University College Dublin, Belfield, Dublin 4, Ireland
| | - Eamonn Gormley
- School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland
| | - Cathal Walsh
- Department of Mathematics and Statistics, University of Limerick, Limerick, Ireland
| | - Jim Duggan
- School of Computer Science, National University of Ireland Galway, Galway, Ireland
| | - T Brendan Murphy
- School of Mathematics and Statistics, University College Dublin, Belfield, Dublin 4, Ireland
| | - Philip Nolan
- National University of Ireland Maynooth, Kildare, Ireland
| | - Breda Smyth
- Department of Public Health, Health Service Executive West, Galway, Ireland
| | | | - Conor Teljeur
- Health Information and Quality Authority, George's Court, Dublin 7, Ireland
| | - Martin J Green
- School of Veterinary Medicine and Science, University of Nottingham, Nottingham, UK
| | - Luke O'Grady
- School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.,School of Veterinary Medicine and Science, University of Nottingham, Nottingham, UK
| | - Kieran Culhane
- Central Statistics Office, Ardee road, Rathmines, Dublin, Ireland
| | - Claire Buckley
- COVID-19 Contact Management Programme, Health Service Executive, Dublin, Ireland
| | - Ciara Carroll
- COVID-19 Contact Management Programme, Health Service Executive, Dublin, Ireland
| | - Sarah Doyle
- COVID-19 Contact Management Programme, Health Service Executive, Dublin, Ireland
| | - Jennifer Martin
- COVID-19 Contact Management Programme, Health Service Executive, Dublin, Ireland
| | - Simon J More
- School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.,Centre for Veterinary Epidemiology and Risk Analysis, School of Veterinary Medicine, University College Dublin, Belfield, Dublin, Ireland
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