Time is of the essence: effectiveness of dairy farm control of H5N1 is limited by fast spread

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.