Background: Adding to the global burden of high pathogenicity avian influenza (HPAI) H5N1, five HPAI H7 outbreaks occurred globally in 2024. Of these, three occurred in South-East Australia, with the independent emergence of HPAI H7N9, H7N8 and H7N3, resulting in the destruction of 2 million poultry. Historical data demonstrate that H7 outbreaks in Australia do not occur randomly; rather, there is a strong association between the timing of the previous H7 outbreaks and rainfall patterns in South-Eastern Australia.

Methods: We aimed to address a hypothesis wherein prior to H7 outbreaks in poultry, there was a detectable change in H7 prevalence and/or virus diversity in wild bird populations. We addressed this using virological data from wild captured ducks, hunted ducks, as well as faecal environmental samples collected in South-Eastern Australia from 2020 to 2024. We also interrogated changes in seroprevalence using both a commercial anti-NP ELISA as well as haemagglutinin inhibition (HI) assays against H7.

Results: Despite the collection of thousands of samples, there was only weak evidence to support our hypothesis, which provides strong incentive to evaluate current surveillance approaches for the purposes of risk prediction. However, in alignment with a previous analysis, there is strong support for a relationship between H7 outbreak probability and rainfall patterns across South-East Australia.

Conclusions: Overall, improved understanding of the ecology and evolution of H5 and H7 viruses in wild bird reservoirs is pivotal to global disease preparedness and response.