As bird flu outbreak expands in California, dairy farms report it's worse than they expected

A third farmworker in California has reportedly tested positive for bird flu, potentially marking the 17th human case of H5N1 flu in the US since the virus was detected in cows. Farmers and veterinarians in the state have noted the infection seems more severe, leading to higher cow morbidity and mortality rates. The recent human cases, all involving farmworkers who had contact with infected cattle, have shown mild symptoms, such as conjunctivitis. Health officials anticipate more cases as infections persist.

Despite taking the situation in stride, experts express concern that the outbreak remains uncontrolled and that those working with affected animals might lack adequate protection. Reports suggest the potential for severe health impacts if unchecked. Over 80 herds in California have been affected since August, with cooperative testing efforts identifying more cases swiftly. California is experiencing rates of 50% to 60% herd infection, with cow mortality between 10% and 15%, surpassing figures in other states.

This surge in severity has prompted inquiries into environmental or viral changes influencing these outcomes. Efforts to trace the virus's spread and evolution continue, though limitations in public data sharing hinder comprehensive understanding.

The gene sequences of some infected individuals and cattle have been shared, though they lack critical contextual information like collection date and location, impeding a full grasp of the outbreak's progression. There are calls for more transparency and timely sharing of genetic data to better monitor the virus's development and potential threat escalation.