Endogenous viral mutations, evolutionary selection, and containment policy design

TL;DR

This paper models how viral mutations and containment policies influence the evolution of viruses like COVID-19, revealing that policy design can inadvertently favor more evasive variants and that long-term effects are hard to predict from short-term data.

Contribution

It introduces an epidemiological model incorporating stochastic mutations and antigenic drift, analyzing how containment strategies affect viral evolution and long-term dynamics.

Findings

Containment policies influence viral evolution direction.

High mutation propensity can lead to indefinite circulation.

Short-term success may mask long-term risks.

Abstract

How will the novel coronavirus evolve? I study a simple epidemiological model, in which mutations may change the properties of the virus and its associated disease stochastically and antigenic drifts allow new variants to partially evade immunity. I show analytically that variants with higher infectiousness, longer disease duration, and shorter latent period prove to be fitter. "Smart" containment policies targeting symptomatic individuals may redirect the evolution of the virus, as they give an edge to variants with a longer incubation period and a higher share of asymptomatic infections. Reduced mortality, on the other hand, does not per se prove to be an evolutionary advantage. I then implement this model as an agent-based simulation model in order to explore its aggregate dynamics. Monte Carlo simulations show that a) containment policy design has an impact on both speed and direction of viral evolution, b) the virus may circulate in the population indefinitely, provided that containment efforts are too relaxed and the propensity of the virus to escape immunity is high enough, and crucially c) that it may not be possible to distinguish between a slowly and a rapidly evolving virus by looking only at short-term epidemiological outcomes. Thus, what looks like a successful mitigation strategy in the short run, may prove to have devastating long-run effects. These results suggest that optimal containment policy must take the propensity of the virus to mutate and escape immunity into account, strengthening the case for genetic and antigenic surveillance even in the early stages of an epidemic.