Deadly Bird Flu Virus Found in Pasteurized Milk

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Deadly Bird Flu Virus Found in Pasteurized Milk
Deadly Bird Flu Virus Found in Pasteurized Milk. Credit | Getty images

United States: Researchers reported on Friday that after treating raw milk samples that had been tipped with high concentrations of the avian flu virus with a conventional pasteurization procedure, minute levels of infectious virus remained detectable.


Implications for Milk Safety

The study’s American authors state that because the results are based on laboratory experiments, no inferences on the safety of the country’s milk supply should be made based on them.

Rocky Mountain Laboratories is home to the National Institute of Allergy and Infectious Diseases (NIAID) of the government.

Raw milk from cows infected with H5N1 influenza may have a different composition or contain virus inside of cells, which may alter heat effects, according to the researchers. This is in contrast to the spiked raw milk with virus floating freely utilized in the study.

In March, it was discovered that dairy cows in the United States had avian flu. Based on an analysis of pasteurized retail milk samples, the US Food and Drug Administration calculated that there were viral strands in around 25% of the country’s milk supply. It is safe to consume pasteurized milk, according to the government.

Study Context and Methodology

The virus utilized in the studies was extracted from the lungs of a deceased mountain lion, combined with raw, unpasteurized cow milk samples, and heated for varying lengths of time at 63 degrees Celsius (145.4 degrees Fahrenheit) and 72 degrees Celsius (161.6 degrees Fahrenheit).

Findings on Virus Survival

Very minute levels of infectious virus were identified in one of three samples following treatment at 72 degrees C for 20 seconds, which is five seconds longer than the industry norm for pasteurization at that temperature, the research said.

If the original viral levels were high enough, the researchers conclude that “this finding indicates the potential for a relatively small but detectable quantity of H5N1 virus to remain infectious in milk after 15 seconds at 72 degrees C.”

Real-World Pasteurization Differences


Treatment at 63 degrees C resulted in a significant drop in infectious H5N1 virus levels in 2.5 minutes, according to the researchers. This suggests that the industry standard pasteurization of 30 minutes at that temperature would eradicate infectious virus.

Uncertain Health Impact

The researchers noted that the conditions under which they conducted their experiments were different from those of large-scale industrial pasteurization procedures for raw milk, and that in order to confirm their findings, contaminated milk must be directly measured using commercial pasteurization apparatus.


The researchers noted that it is still unclear if consuming milk contaminated with the active H5N1 virus may make people sick.

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