SACRAMENTO, Calif. (AP) — The explosive spread of H5N1 bird flu through California’s dairy industry has experts questioning federal officials’ understanding of how the virus is transmitted, even as cases continue to mount.
Since late August, the virus has infected 659 of California’s 984 dairy herds, with about half those cases emerging in the last month alone. The surge prompted Governor Gavin Newsom to declare a state of emergency Wednesday.
“While some farmers may have been less strict” in following USDA precautions, “I personally know a fair number of producers that pulled out all the stops, followed every suggestion, came up with novel protections of their own,” said Mike Payne, a veterinarian at UC Davis’ Western Institute for Food Safety and Security. “They still got infected.”
The USDA maintains that the virus primarily spreads through contaminated equipment and clothing. However, scientists like Seema Lakdawala, associate professor at Emory University School of Medicine, question this explanation.
“It’s just not an efficient transmission route for the virus to go from a porous surface like your clothes up into the mammary gland of a cow,” Lakdawala said. She suggests worker infections and asymptomatic cattle movement between farms may play larger roles.
California State Veterinarian Annette Jones confirmed Friday that 40 research projects are underway to identify additional transmission routes. “We know for sure this virus can travel in a livestock trailer,” Jones said. “But sometimes it just seems like something else is causing the spread as well.”
The outbreak has significant human health implications. Sixty-one human cases have been confirmed nationally this year, mostly among California dairy workers. On Wednesday, the CDC reported the first severe U.S. case in Louisiana, where an individual contracted the virus from infected backyard poultry.
In response, the USDA launched a mandatory national milk testing program December 6. “It’s a combination of these things that compelled us to increase the testing and to make it national,” said Eric Deeble, USDA’s acting senior adviser for H5N1 response.
Worker advocacy groups are calling for additional protections. “Right now it’s a bad gamble for workers,” said Elizabeth Strater of United Farm Workers, urging compensation for testing and sick leave to encourage reporting.
The USDA has confirmed 866 infected herds across 16 states since March, though experts believe the actual number is higher due to limited testing. Some worry the delayed response has allowed the virus to become entrenched.
“There’s more pressure now to solve these questions than there probably was in April or May when we could have maybe actually contained the outbreak,” Lakdawala said.
