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Reports of H5N1 bird flu outbreaks at California dairy herds are continuing to rise as the nation's largest milk producer scrambles to contain the spread.

On Monday, officials reported that the number of infected dairy herds in the Central Valley had doubled over the weekend, rising from 17 to 34.

A spokesman for the California Department of Food and Agriculture said they expect more cases to be announced in the coming days and weeks, as testing continues.

With roughly 1,100 dairy herds in California—and 90% located in the San Joaquin Valley—concern is palpable, say industry insiders. Outbreaks interrupt milk production at affected dairies. Not only are the infected herds quarantined, but special testing must be conducted at nearby dairy farms as well.

"Farmers are genuinely worried about the virus and do not feel it's under control," said Anja Raudabaugh, CEO of Western United Dairies, the trade association of California dairy farmers. She added the industry is hoping a vaccine for cows will be developed "that would protect our animals" and be compliant under trade agreements.

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