Epidemic spreading under mutually independent intra- and inter-host pathogen evolution

Area of Science:

• Epidemiology
• Evolutionary Biology
• Mathematical Modeling

Background:

• Epidemic dynamics are often simplified using the basic reproduction number (R0).
• Pathogen evolution during spread can alter R0, potentially causing mutation-driven pandemics.
• Predicting pandemic emergence requires understanding coupled spread and evolution.

Purpose of the Study:

• To develop a modeling framework integrating inter-host spreading and intra-host evolution.
• To investigate how pathogen mutation dynamics influence pandemic phase transitions.
• To identify conditions enabling initially non-pandemic pathogens to spread widely.

Main Methods:

• Coupling network-based epidemic spreading models with evolutionary dynamics.
• Analyzing the impact of mutation rates and selection forces on pandemic potential.
• Defining a phase diagram influenced by both epidemic and evolutionary timescales.

Main Results:

• Mutations can fundamentally alter pandemic phase diagrams, even with independent selection.
• Pandemic transitions depend on R0 and the balance between epidemic and evolutionary timescales.
• A critical window exists where initially sub-pandemic pathogens can achieve widespread prevalence through mutation.

Conclusions:

• The interplay between pathogen evolution and epidemic spread is crucial for predicting pandemic emergence.
• Mutation speed critically influences whether a pathogen can achieve widespread prevalence.
• Understanding these coupled dynamics can inform public health strategies against evolving pathogens.