Key Environmental Factors Predict Outbreaks of Avian Flu in Europe

Certain local environmental conditions—such as minimum autumn temperatures, winter water levels in lakes and ponds, and the presence of mute swans (Cygnus olor)—could prove crucial for forecasting highly pathogenic avian influenza (HPAI) outbreaks in Europe.

The study, published in Scientific Reports, is based on a machine learning model trained using characteristics from European HPAI outbreaks this century. The findings may enhance future monitoring efforts.

Outbreaks of highly pathogenic avian influenza (HPAI) pose significant threats to both animal and public health. A surge in HPAI outbreaks across the Northern Hemisphere during 2022 was linked with more cases of avian influenza virus infections in mammals, increasing the risk of spillover events into humans. Understanding the factors contributing to HPAI outbreaks is essential for preventing such occurrences.

Lead researcher Joacim Rocklöv and colleagues used a machine learning model trained on the characteristics of all reported European HPAI outbreaks between 2006 and 2021. The analyzed factors included seasonal temperature, precipitation, local wild bird populations, farmed poultry density, vegetation density, and water levels in lakes. They validated their model using outbreak data from 2022 and 2023.

The analysis revealed that the lowest autumn temperatures had a significant impact on outbreak likelihood, with regional variations. In some regions, warmer minimum autumn temperatures correlated with higher outbreak risk, while in others, they correlated with lower risk. Cold winter and spring temperatures also increased outbreak risk.

Conversely, low vegetation density from October to December, and abnormally low water levels in lakes between January and March, were linked to a reduced likelihood of outbreaks. The study also identified that local populations of mute swans were associated with higher outbreak risks.

The researchers suggest these findings could improve the targeting of regional HPAI surveillance programs across Europe, helping to identify outbreaks at their earliest stages.