Enlarge / A glass of fresh raw milk in the hand of a farmer. (credit: Getty | Pierre Crom)

To drink raw milk at any time is to flirt with dangerous germs. But, amid an unprecedented outbreak of H5N1 bird flu in US dairy cows, the risks have ratcheted up considerably. Health experts have stepped up warnings against drinking raw milk during the outbreak, the scope of which is still unknown.

Yet, raw milk enthusiasts are undaunted by the heightened risk. The California-based Raw Milk Institute called the warnings "clearly fearmongering." The institute's founder, Mark McAfee, told the Los Angeles Times this weekend that his customers are, in fact, specifically requesting raw milk from H5N1-infected cows. According to McAfee, his customers believe, without evidence, that directly drinking high levels of the avian influenza virus will give them immunity to the deadly pathogen.

Expert Michael Payne told the LA Times that the idea amounts to "playing Russian roulette with your health." Payne, a researcher and dairy outreach coordinator at the Western Institute for Food Safety and Security at UC Davis, added, "Deliberately trying to infect yourself with a known pathogen flies in the face of all medical knowledge and common sense."

Enlarge / Holstein dairy cows in a freestall barn. (credit: Getty | )

The US Department of Agriculture this week posted an unpublished version of its genetic analysis into the spillover and spread of bird flu into US dairy cattle, offering the most complete look yet at the data state and federal investigators have amassed in the unexpected and worrisome outbreak—and what it might mean.

The preprint analysis provides several significant insights into the outbreak—from when it may have actually started, just how much transmission we're missing, stunning unknowns about the only human infection linked to the outbreak, and how much the virus continues to evolve in cows. The information is critical as flu experts fear the outbreak is heightening the ever-present risk that this wily flu virus will evolve to spread among humans and spark a pandemic.

But, the information hasn't been easy to come by. Since March 25—when the USDA confirmed for the first time that a herd of US dairy cows had contracted the highly pathogenic avian influenza H5N1 virus—the agency has garnered international criticism for not sharing data quickly or completely. On April 21, the agency dumped over 200 genetic sequences into public databases amid pressure from outside experts. However, many of those sequences lack descriptive metadata, which normally contains basic and key bits of information, like when and where the viral sample was taken. Outside experts don't have that crucial information, making independent analyses frustratingly limited. Thus, the new USDA analysis—which presumably includes that data—offers the best yet glimpse of the complete information on the outbreak.