Demographic changes and behavioural responses shape vulnerability to infectious disease outbreaks
6 affiliations
- 1Mathematical Institute, University of Oxford, Oxford, United Kingdom
- 2Department of Mathematics, Konkuk University, Seoul, Republic of Korea
- 3Busan Centre for Medical Mathematics, National Institute for Mathematical Sciences, Busan, Republic of Korea
- 4Saw Swee Hock School of Public Health, National University of Singapore, Singapore
- 5Department of Infectious Disease Epidemiology and Dynamics, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
- 6Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea
Abstract
Demographic shifts are reshaping population age structures worldwide, with implications for infectious disease dynamics. Since contact patterns, susceptibility and infectiousness often vary by age, the risk that pathogen introductions initiate a substantial outbreak depends on the population’s age distribution and associated behavioural characteristics. We develop an age-structured mathematical model to estimate the risk that a single pathogen introduction leads to sustained transmission (the probability of a major outbreak) under long-term demographic transitions, incorporating changes in age-specific contact patterns and behavioural adaptation (specifically, extended workforce participation in an ageing society). Using the Republic of Korea (projected to become the world’s oldest population by 2050) as a case study, we show that population ageing may reduce the probability of a major outbreak due to older individuals’ lower contact rates. However, this effect is attenuated for pathogens with increasing susceptibility or infectiousness with age, and by factors such as later retirement that increase the number of contacts that older individuals have. These findings demonstrate that, while outbreak risks are affected by demographic changes, they are further modified by associated behavioural responses, highlighting the importance of accounting for demographic and socio-behavioural context when assessing future infectious disease outbreak risks. Author summary: In the early stages of an infectious disease outbreak, the risk that initial cases lead to substantial transmission is shaped by a range of factors including the characteristics of the host population. Demographic changes, such as population ageing, are transforming societies worldwide, yet their implications for infectious disease emergence remain unclear. Here, we show that population ageing may reduce the likelihood that imported infections trigger major infectious disease outbreaks due to lower contact rates among older individuals compared to younger individuals. However, this effect depends on how susceptibility, infectiousness and host behaviour vary with age. For example, if future older adults have increased social connectedness (e.g., due to a higher retirement age), then decreases in the outbreak risk may be offset. These findings underscore the need to account for demographic and socio-behavioural factors, in addition to biological factors, when assessing future outbreak risks and designing robust public health strategies, particularly in societies undergoing rapid demographic change.
Versions
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BibTeX
@article{evans2026demographic,
title = {{Demographic changes and behavioural responses shape vulnerability to infectious disease outbreaks}},
author = {Abbie Evans and William S. Hart and Eunok Jung and Kyeongah Nah and Karla Bonic-Babic and Sung-mok Jung and Robin N. Thompson},
journal = {PLOS Computational Biology},
year = {2026},
month = oct,
doi = {10.1371/journal.pcbi.1014319},
url = {https://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1014319},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Demographic changes and behavioural responses shape vulnerability to infectious disease outbreaks
AU - Abbie Evans
AU - William S. Hart
AU - Eunok Jung
AU - Kyeongah Nah
AU - Karla Bonic-Babic
AU - Sung-mok Jung
AU - Robin N. Thompson
PY - 2026
DA - 2026/10/01
JO - PLOS Computational Biology
DO - 10.1371/journal.pcbi.1014319
UR - https://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1014319
AB - Demographic shifts are reshaping population age structures worldwide, with implications for infectious disease dynamics. Since contact patterns, susceptibility and infectiousness often vary by age, the risk that pathogen introductions initiate a substantial outbreak depends on the population’s age distribution and associated behavioural characteristics. We develop an age-structured mathematical model to estimate the risk that a single pathogen introduction leads to sustained transmission (the probability of a major outbreak) under long-term demographic transitions, incorporating changes in age-specific contact patterns and behavioural adaptation (specifically, extended workforce participation in an ageing society). Using the Republic of Korea (projected to become the world’s oldest population by 2050) as a case study, we show that population ageing may reduce the probability of a major outbreak due to older individuals’ lower contact rates. However, this effect is attenuated for pathogens with increasing susceptibility or infectiousness with age, and by factors such as later retirement that increase the number of contacts that older individuals have. These findings demonstrate that, while outbreak risks are affected by demographic changes, they are further modified by associated behavioural responses, highlighting the importance of accounting for demographic and socio-behavioural context when assessing future infectious disease outbreak risks. Author summary: In the early stages of an infectious disease outbreak, the risk that initial cases lead to substantial transmission is shaped by a range of factors including the characteristics of the host population. Demographic changes, such as population ageing, are transforming societies worldwide, yet their implications for infectious disease emergence remain unclear. Here, we show that population ageing may reduce the likelihood that imported infections trigger major infectious disease outbreaks due to lower contact rates among older individuals compared to younger individuals. However, this effect depends on how susceptibility, infectiousness and host behaviour vary with age. For example, if future older adults have increased social connectedness (e.g., due to a higher retirement age), then decreases in the outbreak risk may be offset. These findings underscore the need to account for demographic and socio-behavioural factors, in addition to biological factors, when assessing future outbreak risks and designing robust public health strategies, particularly in societies undergoing rapid demographic change.
SN - 1553-7358
ER -