What makes deadly bird flu spread between migrating birds, and on to poultry?

Embargoed until: Publicly released: 2026-08-26 09:01

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International scientists say deadly bird flu spreads most easily among migratory birds when it passes between individuals rapidly, infections last a long time, when big groups of birds congregate at stopover sites, and when individuals of the same species use differing migration routes. The number of infections in migratory birds and the risk to poultry are mainly linked to characteristics of the virus, they say, but migratory behaviour affects outbreak timing, the length of outbreaks, and where outbreaks occur. The findings suggest wild birds' patterns of movement should be considered when predicting the risk of bird flu outbreaks, the authors conclude.

News release

From: The Royal Society

Determinants of highly pathogenic avian influenza spread during bird migration

This study aimed to identify the conditions under which migratory waterfowl could most strongly contribute to the spatial and temporal dynamics of HPAI and the resulting infection risk. Using an agent-based model we found that migratory birds contribute most under conditions of high bird-to-bird transmission rate, long infectious periods, greater aggregation of birds at stopover sites, and lower overlap in migratory routes among individuals. Viral traits strongly shaped infection prevalence in waterfowl and incursion risk to poultry, whereas migratory behaviour more strongly shaped outbreak timing, maintenance, and spatial distribution. These results suggest that a few viral traits and migration behaviours shape much of infection dynamics.

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Journal/
conference: Royal Society Open Science

Research:Paper

Organisation/s: University of Bern, Switzerland

Funder: The study was funded by the European Union under grant agreement (101084171) - (Kappa-Flu).

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