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Highly Pathogenic Avian Influenza Genes Found in Dairy Herds Across the US
The recent report by the Food and Drug Administration revealed a concerning trend in the dairy industry. Approximately 20 percent of retail milk samples across the nation tested positive for genetic remnants of the highly pathogenic avian influenza (HPAI) virus H5N1. Although retail milk remains safe for consumption, this discovery indicates a broader spread of the virus within dairy herds than was previously recognized.
Testing Methods and Implications
The FDA employed quantitative polymerase chain reaction (qPCR) to detect genetic fragments of the virus in retail milk. However, it is essential to note that qPCR can only identify the presence of genetic material rather than live virus particles. In the case of pasteurized milk, these genetic snippets likely originate from virus particles destroyed during the pasteurization process.
To further validate the effectiveness of pasteurization, the FDA plans to conduct egg inoculation tests, a gold standard for detecting live viruses. These tests aim to confirm the absence of live virus in milk samples. According to the director of the National Institute of Allergy and Infectious Diseases, Jeanne Marrazzo, no live virus has been identified in federal lab tests so far.
Past studies have shown that pasteurization, particularly in eggs, effectively destroys HPAI. While concerns regarding the safety of commercial milk are minimal, the potential widespread prevalence of bird flu in dairy herds raises alarm within the agricultural sector.
Significance of Findings
Despite the FDA confirming infections in only 33 herds across eight states, the positive samples from retail milk indicate a higher proportion of positive results in areas with infected herds. With thousands of dairy herds in the US, these findings suggest that infections may be overlooked, indicating a potential spread of the virus. The 20 percent positive rate does not imply that a fifth of all cows are affected, as milk is pooled for distribution. However, it is unlikely that infections are restricted to the identified 33 herds.
A recent report from The New York Times revealed that a dairy herd in North Carolina, despite testing positive for bird flu, showed no symptoms of the infection. This asymptomatic spread among cows complicates efforts to contain and monitor the virus, potentially leading to more undetected cases.
Responding to this concern, the USDA has issued a federal order mandating dairy cattle to undergo H5N1 testing before crossing state lines. While the public risk remains low according to the Centers for Disease Control and Prevention, experts caution that increased transmission among mammals, especially those in close contact with humans, could heighten the risk of viral evolution and potential transmission to people.
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