California Reports 6 Confirmed Human Bird Flu Cases, 5 Unconfirmed

The California Department of Public Health (CDPH) reported that a total of six human bird flu cases have been confirmed in California. The cases are all in Central Valley individuals who had direct contact with infected dairy cattle and were confirmed after additional testing by the U.S. Centers for Disease Control and Prevention (CDC). As CMM previously reported, the CDC confirmed the first two three human cases in the state on Oct. 3. ​ ​

Two of the human cases originated from the same Central Valley farm, where both individuals had extensive exposure to infected dairy cattle. Given the amount of exposure to infected cows, evidence continues to suggest only animal-to-human spread of the virus in California, CDPH said. 

Based on CDC’s genomic sequencing of California’s first two human bird flu cases, no evidence suggests the virus has an increased ability to infect or spread between people or reduced susceptibility to antiviral medications. 

All six individuals with confirmed cases of bird flu have experienced mild symptoms, including eye redness or discharge (conjunctivitis). All have been treated according to CDC guidance and none of the individuals have been hospitalized. 

In addition to the six confirmed cases, CDPH has also been notified of five additional possible human case, also in the Central Valley. Those specimens have been sent to CDC for confirmatory testing. 

While the risk to the public remains low, additional human cases of bird flu are expected to be identified and confirmed in California among individuals who have regular contact with infected dairy cattle. CDPH continues to work closely with local health jurisdictions to identify, track, test, confirm, and treat possible and confirmed human cases of bird flu. 

On Oct. 11, the CDC reported 20 human cases of bird flu infection have been recorded in the U.S. this year; 21 in total since 2022. Ten of these cases were associated with exposure to bird flu-infected poultry and nine were associated with exposure to sick or infected dairy cows. The source of the exposure in one case, which was reported by Missouri on Sept. 6, is pending.

Going forward, CDC will track and report confirmed cases, by state and source of exposure, in a table on its website. The CDC has allocated more than 100,000 doses of seasonal flu vaccine to 12 states with dairy herds that have tested positive for bird flu. This is part of a CDC initiative announced this summer to provide a number of supplemental free seasonal flu vaccines to farm workers across states affected by bird flu to prevent the spread of seasonal flu in these communities and safeguard public health.

On the animal health side, U.S. Department of Agriculture (USDA) reported that 300 dairy cow herds in 14 U.S. states have confirmed cases of bird flu virus infections as of Oct. 9. The number of affected herds continues to grow nationally, fueled by increases in California. The USDA reported 100 affected dairy herds in California as of Oct. 11. USDA reported  that since April 2024, bird flu has been detected in 36 commercial flocks and 26 backyard flocks, for a total of 18.75 million birds affected.

As part of CDC’s Farmworker Enhanced Surveillance Program (FWESP), CDC is working with pharmacy networks eTrueNorth and Walgreens on a pilot program to provide free testing of symptomatic persons in California and one other state initially that have confirmed bird flu infections in people, poultry, or livestock.