A person who came into contact with cattle at a dairy farm is Merced County‘s first confirmed human case of H5N1 bird flu infection this year, public health officials said Monday.

The case was detected based on symptoms from direct exposure and confirmed by laboratory test results, according to a Merced County news release.

Officials said the level of risk to the public is low. Those people who were exposed to the infected cattle have been notified and are actively being monitored.

As of Oct. 18, the California Department of Health reported the number of humans with bird flu was 13. All of those individuals came into contact with infected dairy cattle.

Dairies in the Central Valley have been overwhelmed by the virus. In some cases, the situation is so severe that dairies have been inundated by the large volume of cattle carcasses.

The disease is also extremely contagious and highly fatal to birds. The virus renders all meat and eggs from the flock unsafe for human consumption. Because of the virus, millions of birds have been euthanized at poultry facilities in Merced County and California.

Humans can be infected with the virus by coming into direct contact with infected birds, cattle or other animals, even if they are dead.

It is also unsafe to come into contact with contaminated bedding, feed, water troughs, and other contaminated surfaces.

The risk of human infection of bird flu is low, and human-to-human transmission is rare, according to the release.

CDPH recommends that personal protective equipment, or PPE, such as eye protection (face shields or safety goggles), respirators (N95 masks), and gloves be worn by anyone working with animals or materials that are infected or potentially infected with the bird flu virus. Wearing PPE helps prevent infection.

Pasteurized milk and dairy products continue to be safe to consume, as pasteurization is fully effective at inactivating the bird flu virus.

CDPH has helped coordinate and support outreach to dairy producers and farm workers on preventive measures that have helped keep human cases low in other states with bird flu outbreaks. CDPH continues to support local health departments in distributing PPE from state and federal stockpiles directly to affected dairy farms, farmworker organizations, poultry farm workers, those who handle raw dairy products, and slaughterhouse workers. To protect California farm workers from bird flu, during the last four months CDPH has distributed more than 400,000 respirators, 1.4 million gloves, 170,000 goggles and face shields, and 168,000 bouffant caps. 

In addition, CDPH is working closely with local public health laboratories and local health departments to provide health checks for exposed individuals and ensure testing and treatment are available when needed. As one of the 14 states with infected dairy herds, California also received 5,000 additional doses of seasonal flu vaccine for farm workers from the CDC. Those doses will go to local health departments with the highest number of dairy farms.  

CDPH has been tracking bird flu and making preparations for a possible human infection since the state’s first detection in poultry in 2022. CDPH partners closely with the California Department of Food & Agriculture (CDFA) on a broad approach to protect human and animal health. CDPH and the CDC use both human and wastewater surveillance tools to detect and monitor for bird flu, and work closely with local health departments to prepare, prevent, and lessen its impact on human health. 

People exposed to infected animals should monitor for the following symptoms for 10 days after their last exposure: eye redness (conjunctivitis), cough, sore throat, runny or stuffy nose, diarrhea, vomiting, muscle or body aches, headaches, fatigue, trouble breathing, and fever. If they start to feel sick, they should immediately isolate, notify their local public health department, and work with public health and health care providers to get timely testing and treatment. 

CDPH recommends that all Californians — especially workers at risk for exposure to bird flu — receive a seasonal flu vaccine. Although the seasonal flu vaccine will not protect against bird flu, it can decrease the risk of being infected with both viruses at the same time and reduce the chance of severe illness from seasonal flu. 

- The Merced Focus contributed to this report.