California is grappling with a growing outbreak of H5N1 bird flu that is taking a devastating toll on dairy cows in the Central Valley. Veterinary experts and industry observers are alarmed as cattle deaths have far exceeded initial expectations. While dairy operators had been prepared for a mortality rate of around 2%, reports suggest that 10% to 15% of infected cattle are dying, threatening both the health of herds and the livelihoods of farmers.

The situation has become more dire as the virus has spread to 56 dairy farms, with the hardest hit regions being Tulare and Fresno counties, the heart of California’s dairy production. Tulare County alone is home to more than 600,000 dairy cows and accounts for 30% of the state’s milk output. 

The outbreak’s impact has been so severe that milk production in affected herds has dropped to just 60% to 70% of normal levels, with some animals unable to fully recover after infection.

The virus has not only affected cows but has also led to California’s first two confirmed human cases of H5N1 among dairy workers. The workers, who contracted the virus while handling infected cows, experienced mild symptoms, including eye redness, but have since recovered. Health officials continue to monitor the situation, and while they maintain that the risk to the general public remains low, the potential for the virus to mutate or spread further is a significant concern.

The outbreak has taken an unexpected toll on California’s dairy industry, which is already contending with other challenges, such as extreme heat. 

High temperatures in the Central Valley have compounded the stress on infected cows, leading to complications like bacterial pneumonia and digestive issues that further increase mortality rates. Veterinarians working in the region, including Dr. Maxwell Beal, have reported that the virus is more severe than anticipated, with many cows dying from complications adjacent to the flu, such as bloat and pneumonia.

Beal noted that the combination of heat stress and the virus’s impact on the respiratory system has made it difficult for many cows to survive. “The animals really don’t do well,” Beal said. “It’s more serious than we had been led to believe.” He and other veterinarians are working to manage the outbreak by ensuring cows are well-hydrated and treating them with medications to reduce fever and discomfort, but the virus is proving difficult to control.

Adding to the complexity of the situation is the challenge of understanding how the virus spreads and how long it stays in herds. In some cases, cows have continued to shed the virus for weeks, and there have been anecdotal reports of cows being reinfected, though this has not yet been confirmed by testing.

While the virus has devastated herds and impacted dairy production, officials are reassuring the public that the nation’s dairy supply remains safe. 

The situation is evolving, and it remains to be seen whether the measures being taken will be enough to contain the outbreak.