Canalization of the evolutionary trajectory of the human influenza virus

TL;DR

This study uses a large-scale model to demonstrate that influenza virus evolution follows a predictable, canalized path primarily along a single antigenic axis, aligning with observed epidemiological and genetic patterns.

Contribution

It introduces a Euclidean antigenic space model that explains the canalized and predictable evolution of influenza A (H3N2) virus.

Findings

Evolution along a single antigenic axis causes rapid population turnover.

Model behavior matches epidemiological, antigenic, and genealogical data.

Evolutionary trajectory is surprisingly repeatable and predictable.

Abstract

Since its emergence in 1968, influenza A (H3N2) has evolved extensively in genotype and antigenic phenotype. Antigenic evolution occurs in the context of a two-dimensional 'antigenic map', while genetic evolution shows a characteristic ladder-like genealogical tree. Here, we use a large-scale individual-based model to show that evolution in a Euclidean antigenic space provides a remarkable correspondence between model behavior and the epidemiological, antigenic, genealogical and geographic patterns observed in influenza virus. We find that evolution away from existing human immunity results in rapid population turnover in the influenza virus and that this population turnover occurs primarily along a single antigenic axis. Thus, selective dynamics induce a canalized evolutionary trajectory, in which the evolutionary fate of the influenza population is surprisingly repeatable and hence, in theory, predictable.