Flu Virus Persists in Refrigerated Raw Milk for Up to 5 Days: Study

Introduction
Raw milk, often promoted as a natural and nutrient-rich alternative to pasteurized dairy, may pose hidden dangers. A new study from Stanford University, published in Environmental Science & Technology Letters on December 12, reveals that the influenza virus can remain infectious in refrigerated raw milk for up to five days. These findings emerge amidst rising concerns about bird flu outbreaks in dairy cattle and the potential for new pandemics.

Key Findings on Flu Virus in Raw Milk
The researchers focused on the survival of the H1N1 PR8 strain of human influenza virus in raw cow’s milk stored at typical refrigeration temperatures. The virus remained infectious for up to five days, raising concerns about potential transmission through raw milk consumption and contamination of dairy facilities.

Additionally, influenza RNA—genetic material of the virus—was detectable in raw milk for at least 57 days. While RNA itself does not pose a health risk, its persistence complicates environmental surveillance and food safety assessments. In contrast, pasteurization eliminated infectious influenza and reduced viral RNA levels by 90%, though traces of RNA still remained.

Health Risks of Raw Milk
More than 14 million Americans consume raw milk annually, often citing benefits such as higher nutrient retention and improved gastrointestinal health. However, raw milk is not heat-treated to eliminate harmful pathogens, making it a potential carrier of bacteria like E. coli and Salmonella.

The FDA and CDC have linked raw milk to over 200 illness outbreaks, emphasizing that vulnerable groups—children, pregnant women, the elderly, and immunocompromised individuals—face significant risks.

Implications for Public Health
The study’s findings underscore the urgent need for enhanced monitoring systems as bird flu continues to spread among livestock. Recent detections of bird flu in cattle have raised questions about its transmission through milk and dairy products.

The prolonged presence of viral RNA in raw and pasteurized milk also highlights the importance of refining testing methods used for pathogen surveillance. Researchers recommend leveraging wastewater monitoring systems to detect zoonotic pathogens, including avian influenza, in agricultural settings.

Why This Matters Now
Influenza viruses infect over 40 million people in the U.S. annually, leading to more than 50,000 deaths. While bird flu has not yet posed significant risks to humans, its potential to mutate remains a concern.

The Stanford study builds on earlier research using wastewater to track avian influenza. This innovative approach has proven effective in detecting virus activity in dairy waste and nearby cattle populations.

Conclusion
The study highlights the need for strict food safety measures, including pasteurization, to mitigate the risks associated with raw milk consumption. With bird flu spreading among livestock, improving surveillance and preventive strategies becomes critical for protecting public health and preventing future pandemics.