Pasteurisation temperatures effectively inactivate influenza A viruses in milk

Area of Science:

• Veterinary Virology
• Food Safety
• Public Health

Background:

• A novel H5N1 highly pathogenic avian influenza virus (HPAIV) emerged in US dairy cattle in late 2023.
• High viral titers in milk raised concerns about milk as a potential human transmission route.
• The efficacy of standard milk pasteurization against influenza viruses was unknown.

Purpose of the Study:

• To assess the heat inactivation of various influenza viruses in milk.
• To determine if pasteurization effectively inactivates H5N1 HPAIV in milk.

Main Methods:

• Evaluated heat inactivation of human and avian influenza A viruses (IAVs), influenza D virus, and recombinant IAVs in milk.
• Tested viral inactivation at pasteurization temperatures (63°C and 72°C).
• Assessed H5N1 HPAIV inactivation in milk under comparable conditions.

Main Results:

• Viral infectivity was rapidly lost and became undetectable at pasteurization temperatures before recommended holding times.
• H5N1 HPAIV in milk was effectively inactivated by pasteurization treatments.
• Viral genetic material (RNA) remained detectable after heat treatment, despite loss of infectivity.

Conclusions:

• Standard pasteurization conditions are expected to effectively inactivate H5N1 HPAIV in cows' milk.
• Unpasteurized milk poses a risk for transmitting infectious influenza viruses.
• Milk pasteurization is a critical control measure for ensuring milk safety regarding influenza viruses.