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Social mixing and time use throughout the year: Potential changes in disease transmission and age distribution of
Edwin Van Leeuwen1, Frank G Sandmann1, Rosalind M Eggo2
1Statistics, Modelling and Economics Department, UK Health Security Agency, London, UK; Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, Keppel Street, London, UK.
Insights
Children's susceptibility to respiratory viruses like influenza impacts transmission dynamics. Holiday contact changes can shift infections from children to adults, potentially increasing risk for vulnerable older populations.
Area of Science:
- Epidemiology
- Virology
- Mathematical Modeling
Background:
- Children's varying susceptibility to respiratory viruses influences transmission heterogeneity.
- Natural immunity in adults can alter age-specific disease incidence patterns.
Purpose of the Study:
- To model the impact of seasonal changes in social mixing on respiratory virus transmission.
- To investigate how varying childhood susceptibility affects epidemic dynamics and age distribution of infections.
Main Methods:
- Utilized age-stratified contact rates from national surveys to model time use and social mixing.
- Developed a model to explore changes in reproduction number (R0) and incidence distribution.
- Simulated scenarios with different assumptions of susceptibility in children (0-15 years).
Main Results:
- Seasonal time use changes influenced R0 and the age distribution of respiratory infections.
- During holidays, R0 decreased and incidence shifted from children to adults when adults had natural immunity.
- Reduced childhood susceptibility lessened the impact of holiday contact changes on age distribution.
Conclusions:
- Holiday periods can alter the age distribution of respiratory infections, shifting cases from children to adults.
- Increased intergenerational mixing during holidays may pose risks to older, more vulnerable populations.
- Childhood susceptibility is a critical factor in understanding and managing respiratory virus epidemics.
Abstract:
Susceptibility in children is a key driver of heterogeneity in the transmission of different respiratory viruses. For example, SARS-CoV-2 is associated with low susceptibility in children, while for the influenza and respiratory syncytial viruses it is thought that children have higher susceptibility, because adults will have built up natural immunity. We modelled seasonal changes in time use and social mixing based on age-stratified contact rates using historical nationally-representative surveys. We explored changes in the reproduction number and the age distribution of infections of respiratory diseases during the early phase of an epidemic, for different assumptions of susceptibility in children aged 0-15. Across ages, the estimated R0 and the age distribution of incidence fluctuated due to changes in time use. For the scenarios where adults have acquired natural immunity through past infection R0 fell and relative incidence decreased in children aged 0-15 but increased in other ages during holiday periods. If children were less susceptible than adults these changes were less pronounced. Our modelling findings suggest that changing contacts during the holiday periods may shift the age distribution of cases from children towards adults. Given that severity and deaths rise with age for many diseases, more intergenerational mixing risks the disease moving into the more vulnerable following the holidays even if the absolute number of infections did not increase.
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