AbstractThe emergence of highly pathogenic avian influenza A H5N1in dairy cattle raises many questions related to animal health and changes to the risk of an epidemic in humans. We synthesized information currently published to fit a compartment model of H5N1transmission within a dairy herd. An accompanying web application allows users to run simulations for specific outbreak scenarios. We estimatedR0near 1.2 with a short duration of infectiousness and fast time course of an epidemic within a farm, which we discuss in the context of possible on-farm control strategies. The web application allows users to simulate consequences of an epidemic using herd-specific information, a tool we propose will help inform stakeholders about potential consequences of uncontrolled H5N1spread. Our modeling work has identified several key information gaps that would strengthen our understanding and control of this emerging infectious disease.

The emergence and growth of highly pathogenic avian influenza(HPAI) A(H5N1) in dairy cows poses a growing threat for both the food supply and onward zoonosis to humans. Despite ongoing surveillance and control measures recommended by animal and public health authorities to limit viral spread, new herds continue to report infections. We show here that the continued spread between farms could be explained by the rapid pace of pathogen spread reported within farms, which greatly limits the potential effectiveness of these recommendations. Under reasonable surveillance strategies, we show that the time farms have to mobilize interventions is extremely limited, as few as a couple days and typically less than a week. Our findings suggest that passive surveillance measures, such as detection of H5N1 via weekly bulk milk testing, comes too late such that most infections have already occurred. For current interventions to be valuable, more sensitive and extensive surveillance is needed and an emphasis should be placed on biosecurity practices rather than reactive practices.