Epidemics in Competition: Partial Cross-Immunity.

Area of Science:

• Epidemiology
• Evolutionary biology
• Infectious disease dynamics

Background:

• Pathogen strain competition is crucial for understanding emerging diseases and influenza's antigenic drift.
• Traditional epidemic models often overlook the impact of introduction timing and size on strain competition.

Purpose of the Study:

• To explore how mean-field epidemic models can characterize pathogen strain competition.
• To determine the range of possible epidemic outcomes, including final host sizes and attack rates, for competing strains.

Main Methods:

• Utilizing deterministic mean-field epidemic models.
• Analyzing the competition dynamics between two cross-reacting pathogen strains.
• Investigating outcomes in the limit of near-zero initial infections.

Main Results:

• Mean-field models can define the possible final sizes of susceptible hosts and cumulative attack rates.
• The timing and size of strain introduction significantly influence competition outcomes.
• In a zero-initial-infection limit, outcomes are constrained to a one-dimensional curve.

Conclusions:

• Deterministic mean-field models provide insights into pathogen competition dynamics.
• Introduction parameters are critical for predicting epidemic trajectories and outcomes.
• Further research can refine models to better capture complex competition scenarios.