A new scientific study has revealed that the highly pathogenic avian influenza virus H5N1, commonly known as bird flu, can persist in cheese made from raw milk for extended periods. However, researchers found that certain acidic cheese varieties—such as feta—are capable of inactivating the virus, potentially reducing the risk of transmission through dairy products.

The findings come amid rising global concerns about the spread of H5N1 across livestock and poultry populations, and its sporadic detection in mammals, including humans. The study provides valuable insights into how food production methods and acidity levels can influence the survival of the virus in dairy-based products.

Virus Survival in Raw-Milk Cheese

Scientists conducted detailed laboratory tests to assess how long the H5N1 virus can survive in different types of cheese made from unpasteurized milk. The results showed that the virus remained viable in certain varieties for up to 120 days. This indicates that cheese made from raw milk, especially those with lower acidity levels, could potentially serve as a medium for viral persistence if contaminated milk is used during production.

Pasteurization, a standard process used to heat milk and destroy pathogens, is known to eliminate H5N1 effectively. However, artisanal or farm-made cheeses prepared using raw milk could pose a higher risk, particularly when proper hygiene standards are not maintained.

Acidity as a Key Factor

The study highlighted that acidity plays a crucial role in determining whether the virus survives or dies in cheese. Cheeses with high acid content, such as feta, displayed the ability to inactivate the virus shortly after production. In contrast, varieties with neutral or lower acidity provided an environment that allowed the virus to persist for weeks or even months.

Researchers explained that the pH level of the cheese affects viral stability. Acidic conditions disrupt the virus’s protein structure, making it incapable of infecting cells. This natural antiviral property of certain cheese types could inform future food safety measures and consumer guidelines.

Public Health Implications

The discovery underscores the importance of pasteurization and stringent dairy safety standards, particularly in regions where raw milk cheese production remains popular. Public health experts have emphasized that while the risk of contracting bird flu from consuming cheese is low, contaminated dairy products could still serve as a potential transmission route if safety measures fail.

With the ongoing spread of H5N1 among wild birds, poultry, and some mammals, food safety agencies are closely monitoring dairy supply chains. The new data may lead to revised recommendations for raw milk processing, cheese production, and trade regulations.

Global Context

The H5N1 virus has caused significant outbreaks across continents, affecting millions of birds and leading to occasional human infections, primarily through direct contact with infected animals. While human-to-human transmission remains extremely rare, scientists continue to warn that viral mutations could pose new pandemic threats if left unchecked.

This latest research highlights how even food products—often overlooked in the chain of viral transmission—could influence disease spread dynamics. It also calls attention to the need for stronger biosecurity measures on farms and better education for consumers and producers about the risks associated with raw milk products.