by Henry Miller, Kathleen Hefferon, Genetic Literacy Project
It was three months ago when we wrote about the surge of the H5N1 bird flu strain that had by then already killed tens of millions of birds in various parts of the U.S. and land and marine animals in other countries. Surprising experts, the flu jumped to cows and goats last month. And now it has been detected very high concentrations in raw milk from infected animals, the World Health Organization announced late last week.
Although the finding surprised health officials, they say there is at present little concern that the infected raw milk will make it into the food supply. Dairies must destroy milk from sick cows, and it’s believed that pasteurization would kill the virus in milk from cows that have not yet been identified as ill. Federal officials are advising not to drink raw milk or eat raw milk-based cheese.
Just a few days before, a man working on a Texas dairy farm was diagnosed with illness from the avian flu strain, “The case in Texas is the first case of a human infected by avian influenza by a cow,” said Wenqing Zhang, head of the global influenza program at the WHO. It’s only the second known case in the U.S. of a human contracting the disease.
Spread of H5N1 surprises disease experts
Infections by the current virus strain have been increasing since the 1990s as the world poultry population soared to meet escalating food demand. H5N1 avian flu claimed its first known human victims in 1996-97, in China and Hong Kong, spread to Cambodia in 2003, and then reappeared with a vengeance a decade ago.
According to the WHO, it has killed nearly 60% of the more than 800 people infected between 2003 and 2016. The majority of human H5N1 infections and deaths occurred in Egypt, Vietnam, and Indonesia.
We wrote in January:
Despite limited examples of person-to-person transmission, there are no known examples of widespread, sustained transmission among humans or any mammals for that matter. However, virus evolution called “antigenic shift” could give rise to the emergence of novel viral subtypes able to target mammals.
As often happens in the infectious disease world, circumstances have changed dramatically in just a few months. The discovery of H5N1 bird flu in dozens of herds of dairy cows across the U.S. has sparked worry and a call for more transparency from the government — specifically, the USDA. This strain of bird flu, while not new, had never before been found in cattle. It has now affected herds in eight states, with some cows showing reduced milk production and discolored, viscous milk.
Scientists and public health experts are particularly concerned about two things: the risk of the virus spreading between cows and potentially mutating to readily infect humans (only one case has thus far been found in a dairy worker in Texas); and the paucity of detailed, timely information from the USDA regarding the outbreak.
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