An alarming 14% of raw milk samples taken from states with dairy herd outbreaks contained infectious H5N1 bird flu, according to new testing results released by the FDA.

The researchers took 275 milk samples from bulk storage tanks on farms in four states where dairy cattle are confirmed to be infected by H5N1. The virus was actually detected in 57.5% of the samples, with further testing showing that a quarter of these contained infectious virus.

The results were published in a preprint paper, which has not yet been peer reviewed by external experts for scientific rigor. However, the paper has sparked a significant response from experts around the world, reiterating the dangers of consuming raw milk.

The researchers also artificially spiked milk with infectious H5N1 virus, before heat treating it in a process designed to mimic pasteurization which the standard commercial milk supply goes through before sale, finding that the process was very effective at inactivating the virus, with the researchers stating; “these findings demonstrate that the milk supply is safe.”

The consumption of “raw milk” which has not undergone filtration or heat treatment to remove pathogens has been responsible for several outbreaks of illness including with bacteria such as campylobacter and comes with significant health risks, according to the CDC. Although there are no documented cases yet of humans getting H5N1 by drinking infected raw milk, there is evidence that mice have been infected via drinking cows milk.

The new results come amid a new survey released today which shows that less than half of U.S. adults know that drinking raw milk is more unsafe than drinking milk that has been pasteurized.

The survey, run by researchers at the Annenberg Public Policy Center at the University of Pennsylvania from June 7-10 this year, asked over 1,000 U.S. adults their beliefs about raw milk, finding that only 47% of respondents knew that raw milk was less safe to drink. A further 30% were not sure, 15% thought it was just as safe and 9% of respondents thought it was safer.

“It is important that anyone planning to consume raw milk be aware that doing so can make you sick and that pasteurization reduces the risk of milk-borne illnesses,” said Patrick E. Jamieson, director of the Annenberg Health and Risk Communication Institute at the Annenberg Public Policy Center at the University of Pennsylvania.

The survey also found that 20% of respondents weren’t sure how effective pasteurization is at killing viruses and bacteria and 4% thought it was “not too effective” or “not at all effective.” Adults who were 65 or older and/or college educated were more likely to understand the benefits of pasteurization and also correctly believe that pasteurization does not destroy nutrients in milk.

Some beliefs about raw milk were also different depending on political affiliation, with 57% of Democrats believing that drinking raw milk is more unsafe than drinking pasteurized milk, compared to 37% of Republicans.

“The difference in views of raw milk that we see between Democrats and Republicans is difficult to disentangle from the difference between rural and urban dwellers,” said Kathleen Hall Jamieson, director of the Annenberg Public Policy Center. “Those in rural areas are both more likely to identify as Republicans and to consume raw milk,” said Jamieson.