The emergence of H5N1 clade 2.3.4.4b in dairy cattle raised concerns over the safety of fluid milk. We developed two stochastic quantitative risk assessment models to represent the United States raw and pasteurized fluid milk supply chains and employed these models in baseline, sensitivity, and scenario analysis. Median (5th, 95th percentiles) probabilities of infection per 240-mL pasteurized and farmstore-purchased raw milk serving were 5.68E-15 (1.766E-16, 2.98E-13) and 1.13E-03 (5.16E-06, 3.82E-02), respectively. This metric was highly sensitive to the viral titers in infected cows’ milk. Pasteurization is highly effective at reducing this risk. Bulk tank milk PCR testing is more effective at reducing the probability of infection per raw milk serving than improving the identification and diversion of infected cows’ milk at harvest. These findings emphasize the importance of pasteurization and dairy cow disease surveillance in reducing the risk of H5N1 infection associated with fluid milk consumption.

Summary In this epidemiologic study, the public health risk of human H5N1 infection from drinking raw and pasteurized milk is investigated by use of quantitative risk assessment models.