Speaker
Description
Emergence of high-pathogenicity avian influenza virus (HPAIV) H5 or H7 variants, following infection with low-pathogenicity avian influenza (LPAIV) of several poultry flocks or directly after infection of a single of few flocks within a poultry farm, emphasizes the need for understanding co-circulation dynamics of LPAIV and HPAIV in poultry farms to develop adequate control strategies. Although the transition from LPAIV to HPAIV is a well-documented phenomenon, limited knowledge exists on the epidemiological processes leading to selection of the HPAIV variant following its emergence in a flock. We performed transmission experiments in chickens to assess transmission of field sample containing a mix of both LPAIV and HPAIV and experiments with purified LPAIV and HPAIV variants. We derived quantitative estimates of key epidemiological parameters and developed a mechanistic stochastic Susceptible-Infectious-Recovered model, based on these estimates. We found that if HPAIV randomly emerges within an LPAIV infected chicken within the first 10 days following the start of LPAIV outbreak in a flock, a large fraction of chickens in the flock will become infected with the HPAIV (“major outbreak”) with a probability of 0.9, followed by a gradual decline over subsequent days, resulting in a probability of less than 0.1 at 17 days post-mutation. We discuss the implications for control and surveillance measures of the HPAIV in poultry farms, and how these findings can support policymakers.
