Ancestral process for infectious disease outbreaks with superspreading
Xavier Didelot1, David Helekal2, Ian Roberts3
1School of Life Sciences, University of Warwick, Coventry, United Kingdom; Department of Statistics, University of Warwick, Coventry, United Kingdom.
Journal of Theoretical Biology
|April 15, 2025
Summary
This study introduces a new method to trace infectious disease origins, even in small outbreaks. It calculates the probability of shared infectors using offspring distributions and a novel Omega-coalescent model.
Area of Science:
- Epidemiology
- Mathematical Biology
- Genetics
Background:
- Traditional ancestral models for infectious diseases often assume large population sizes, limiting their applicability to small outbreaks.
- Accurately describing the ancestry of infected individuals in small-scale outbreaks presents a significant challenge.
Purpose of the Study:
- To develop a method for calculating the exact probability of shared infectors among a sample of infected individuals, regardless of outbreak size.
- To introduce a new coalescent model, the Omega-coalescent, for analyzing infectious disease transmission dynamics.
Main Methods:
- Derived exact probabilities for shared infectors (inclusive and exclusive) based on offspring distributions.
- Incorporated these probabilities into a new Lambda-coalescent model, termed the Omega-coalescent.
- Considered both Poisson (no superspreading) and Negative-Binomial (superspreading) offspring distributions.
Main Results:
- Successfully derived exact probabilities for shared infectors in small infectious disease outbreaks.
- Developed and validated the Omega-coalescent model, which accommodates multiple lineage coalescences.
- Demonstrated the utility of the Omega-coalescent by comparing it to existing models.
Conclusions:
- The proposed method and Omega-coalescent model offer a robust framework for inferring ancestry in infectious disease outbreaks of any size.
- The Omega-coalescent model provides a more flexible and accurate approach for studying transmission dynamics, particularly in scenarios with superspreading.
- Advocates for the adoption of the Omega-coalescent model in future infectious disease outbreak investigations.
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