Stability of influenza A H5N1 virus in raw milk cheese

Here we evaluated the stability of highly pathogenic avian influenza (HPAI) H5N1 virus in raw milk cheeses using a mini cheese model prepared with HPAI-spiked raw milk under varying pH levels (pH 6.6, 5.8 and 5.0) and in commercial raw milk cheese inadvertently produced with naturally contaminated raw milk. We observed a pH-dependent survival of the virus, with infectious virus persisting throughout the cheese making process and for up to 60 days of aging in the pH 6.6 and 5.8 cheese groups. Whereas at pH 5.0, the virus did not survive the cheese making process. These findings were validated using the commercial raw milk cheese samples in which infectious virus was detected for up to 60 days of aging. Our study highlights the potential public health risks of consuming raw milk cheese, underscoring the need for additional mitigation steps in cheese production to prevent human exposure to infectious virus.