DELTA-FLU aims to determine the key viral, host-related, and environmental factors that determine the dynamics of avian influenza (AI) in poultry and other host species, with the goal of improving prevention and control strategies against this disease. As a result of rapidly changing dynamics, AI continues to cause unexpected and devastating outbreaks in poultry in the EU, as well as world-wide. Its potential to become pandemic is also of great concern to public health. The key viral, host-related, and environmental factors that drive AI dynamics are poorly understood, which currently impedes the development of effective control and prevention strategies.