# Quantitatively analyzing the relationship between non-pharmaceutical interventions and the direction of virus evolution using a dynamic model

## TL;DR

This study uses a dynamic model to show how non-pharmaceutical interventions influence the evolution of viruses like SARS-CoV-2, affecting their spread and immune evasion.

## Contribution

A novel genetic algorithm-based model is introduced to analyze how NPIs shape viral evolution and epidemic dynamics.

## Key findings

- Strict NPIs reduce virus transmission and mutation, favoring strains with high immune evasion and infectivity.
- Relaxing NPIs increases the risk of recurring epidemics due to ongoing viral mutations.
- Virulence evolution showed no clear trend, consistent with observed patterns in the COVID-19 pandemic.

## Abstract

Since the emergence of COVID-19 in 2019, SARS-CoV-2 has persisted in mutating, giving rise to multiple variants of concern that have triggered several pandemics globally. The evolutionary trajectory of the virus is shaped by a combination of stochastic factors and non-pharmaceutical interventions (NPIs). Investigating the direction of virus evolution and its underlying determinants is crucial for forecasting epidemic trends and formulating scientific responses to emerging infectious diseases.

To delve into the intricate relationship between NPIs and the virus’s transmissibility, virulence, and immune evasion capabilities, as well as to explore the sociological mechanisms driving virus evolution, we developed a genetic algorithm grounded in a population dynamics model. This model simulates the processes of virus mutation and epidemic dissemination, enabling us to analyze the correlation between intervention strategies and the evolutionary path of the virus.

Our study reveals that, under the influence of NPIs, dominant strains capable of widespread transmission within the population exhibit substantially elevated immune evasion capabilities and heightened infectivity. Notably, the evolution of virulence did not display a discernible trend, aligning with the observed epidemic characteristics of COVID-19. It was found that the stricter the implementation of NPIs, the more favorable the conditions for rapidly and thoroughly containing virus transmission and mutation. Conversely, the relaxation of these measures may pose a risk of recurring epidemics fueled by continuous viral mutations.

Presently, the potential emergence and widespread transmission of SARS-CoV-2 variants with increased virulence cannot be discounted. Therefore, it is imperative to continuously monitor the dynamic shifts in the epidemic landscape and the antigenic variations of new variants. Simultaneously, it is necessary to devise and prepare prevention and control strategies to effectively manage outbreaks caused by highly pathogenic variants.