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.

The H5N1 bird flu appears to be stampeding through dairy farms in California, the country's largest milk producer. Over the weekend, the total number of confirmed infected cow herds stunningly doubled, going from 17 last Thursday to 34 Monday morning, according to state and federal officials.

In other H5N1 developments, the FDA's vaccine advisory group said it will discuss the composition of H5 vaccines when it meets next month.

The mandatory testing comes as the total number of infected herds in California has risen to 17. Nationally, officials have announced 218 outbreaks across 18 states. In the last 30 days, however, California has accounted for all but two of the latest outbreaks.

Why it matters: California now accounts for all but two of the nation’s recent H5N1 bird flu outbreaks in livestock over the past 30 days.

Colombia has lifted restrictions on imports of U.S. beef from states where dairy cattle tested positive for bird flu, according to a U.S. Department of Agriculture website. Colombia in April became the only country to officially limit trade in U.

Three more California dairy herds have been infected with H5N1 bird flu. A new case of human infection has also been reported in Missouri.