Avian Influenza Confirmed in 3 Central Valley Dairy Herds

The samples were then submitted to the National Veterinary Services Laboratory (NVSL), where the test results were confirmed today.

No human cases of HPAI have been confirmed in California related to this incident. The California Department of Public Health (CDPH) is working in collaboration with CDFA and will work with local health departments to monitor any individuals who may be exposed to infected animals to ensure prompt clinical and public health interventions, and CDPH would provide official confirmation of any human cases associated with this incident.

“We have been preparing for this possibility since earlier this year when HPAI detections were confirmed at dairy farms in other states,” said CDFA Secretary Karen Ross. “Our extensive experience with HPAI in poultry has given us ample preparation and expertise to address this incident, with workers’ health and public health as our top priorities. This is a tough time for our dairy farmers given the economic challenges they’re facing in a dynamic market, so I want to assure them that we are approaching this incident with the utmost urgency.” 

According to CDPH and the Centers for Disease Control (CDC), this influenza virus is not considered a significant public health threat and the risk to humans is considered low.

The primary concern is for dairy workers who come into close contact with infected dairy cows. As we have learned from recent cases in other states, these workers may be at risk of contracting avian influenza. Public health officials have experience working with agricultural partners and supporting farm workers working with infected poultry to prevent and monitor for infection.

CDPH recommends that PPE (masks, gloves, caps, face shields, and safety goggles) be worn by farm workers and emergency responders when working with animals or materials that are infected or potentially infected with avian influenza. Earlier this summer, CDPH supported a one-time distribution of protective equipment for dairy farm workers and others handling raw dairy products, as well as for slaughterhouse and commercial poultry farmworkers.

CDPH will continue to support dairies with confirmed positive cases with PPE. Furthermore, affected farms can take advantage of a USDA grant that provides financial support for producers that supply PPE to employees.

The CDC has confirmed four human cases of HPAI in dairy workers in other states since April 2024: one each in Texas and Colorado, and two in Michigan.

CDFA is working with public health officials and dairy owners to inform and monitor workers at affected dairies in California, and to assist the dairies with education and resources to protect their workers, including providing PPE. 

For CDC guidance for employees and employers, please visit https://www.cdc.gov/flu/pdf/avianflu/protect-yourself-h5n1.pdf 

California’s supply of milk and dairy foods is safe and has not been impacted by these events. As a precaution, and according to longstanding state and federal requirements, milk from sick cows is not permitted in the public milk supply. Also, pasteurization of milk is fully effective at inactivating the virus, so there is no cause for concern for consumers from milk or dairy products. Pasteurized milk and dairy items, as well as properly handled meat and eggs, continue to be safe to consume. 

The affected dairies have been placed under quarantine on the authority of CDFA’s State Veterinarian, and enhanced biosecurity measures are in place. Sick cows are isolated and are being treated at the dairies; and healthy cows have been cleared to continue shipping milk for pasteurization. Animal movement is being tracked and evaluated, as are other potential introduction pathways. Additional testing will be prioritized according to epidemiologic risk. 

Background on HPAI in California
The HPAI virus has been detected in wild birds in the U.S. since 2022, with occasional transmission into domestic poultry or wild mammals in almost all states, including California. In March, 2024, the first US detection in cattle was confirmed in Texas, most likely due to a single spillover event from wild birds. Since that time, the USDA has linked new detections in cattle to the interstate and regional movement of infected or contaminated livestock, people and equipment. CDFA has been engaged for years with an extensive network of private veterinarians, farmers and ranchers, backyard bird enthusiasts, and local, state and federal partners to actively monitor for this disease in livestock and poultry throughout California. The department has taken steps to reduce the risk of entry of infected dairy cattle into the state, has extensive experience responding quickly and effectively to past detections of HPAI in poultry, and is fully prepared to respond to detections in cattle. 

Most infected livestock and dairy cattle fully recover from an HPAI infection within a few weeks No California domestic poultry flocks are affected by the current incident. 

Avian influenza viruses continue to circulate normally among migratory and wild birds. Monitoring of both wild and domestic bird populations is performed on a continuous basis by multiple public agencies, as well as farmers and ranchers and private bird owners. 

For the most up-to-date information regarding highly pathogenic avian influenza (HPAI) in livestock in California, please visit CDFA – AHFSS – AHB – Highly Pathogenic Avian Influenza (HPAI) H5N1 Virus in Livestock.