Quantitative Microbial Risk Assessment of Human H5N1 Infection From Consumption of Fluid Cow's Milk

Area of Science:

• Food safety
• Epidemiology
• Microbial risk assessment

Background:

• H5N1 avian influenza (H5N1) has spilled over into dairy cattle, raising public health concerns regarding fluid milk safety.
• While no foodborne H5N1 infections have been reported in humans, the virus has infected people and is present in infected cow's milk.

Purpose of the Study:

• To conduct a quantitative microbial risk assessment (QMRA) of human infection risk from consuming raw and pasteurized fluid cow's milk in the US.
• To evaluate the effectiveness of interventions, such as pasteurization and bulk tank milk testing, in mitigating H5N1 infection risk.

Main Methods:

• Utilized stochastic models for a farm-to-table QMRA, incorporating data from the current H5N1 outbreak.
• Modeled infection probabilities for pasteurized, farmstore-purchased raw, and retail-purchased raw milk servings.
• Performed scenario analysis to assess the impact of interventions like bulk tank milk testing.

Main Results:

• Pasteurization was confirmed as highly effective, reducing H5N1 infection risk to negligible levels (median probability of 7.66E-19 per serving).
• Raw milk consumption presented a significantly higher median infection risk (1.56E-7 for farmstore, 1.40E-7 for retail).
• Quantitative real-time reverse transcriptase-polymerase chain reaction (qrRT-PCR) testing of bulk tank milk was identified as an effective risk reduction strategy for raw milk.

Conclusions:

• Pasteurization is a critical control measure for ensuring the safety of fluid milk against H5N1.
• Testing raw milk supplies and understanding consumption patterns are important for public health preparedness.
• Further research is needed on human H5N1 dose-response and raw milk consumption behaviors to refine risk assessments.