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Possible bird flu cases in humans in California rise to 3. They’re all in the Central Valley.

Dairy farms in the United States have seen outbreaks of bird flu among their cattle.
Joe Moore
/
KVPR
Dairy farms in the United States have seen outbreaks of bird flu among their cattle. That now includes farms in the San Joaquin Valley.

This story was updated Saturday, Oct. 6, 2024 at 10 p.m.

FRESNO, Calif. – Three people who had direct contact with cattle infected with bird flu have now either contracted the virus themselves or are suspected of being inected in the Central Valley.

The Tulare County Department of Public Health announced Friday that two of the people were dairy workers in Tulare County, one of the country’s leading dairy regions. Initial reports of bird flu in California residents were announced on Thursday. The California Department of Public Health said only one worker who was in contact with cattle infected with the virus became sick. The department later raised the number to two, but as of Saturday, one more person was suspected of being infected. Tests were being examined.

All three people worked at different farms, and the two who were confirmed to be infected were showing mild symptoms. They were treated with antiviral medications and isolated at home. They showed symptoms such as eye redness or discharge, according to county health officials.

Despite publicly revealing two of the cases were tied to Tulare County, officials are not disclosing which specific dairy farms reported the cases. State and local health officials have been wary of disclosing the locations because of the potential of residents going near the sites and either becoming infected or further transmitting the virus elsewhere.

Avian influenza, which has affected tens of millions of birds nationwide since an outbreak began in 2022, has this year been detected in cattle, and was first reported in a California cow in August. Health officials say they are closely monitoring workers across the state for signs of illness.

People most at risk of catching the virus are those working directly with infected cattle or poultry. California employs on average over 17,000 people in the dairy and milk production industry.

To date, health officials in Tulare County say they’ve distributed over a million pieces of personal protective equipment to workers at over 150 facilities, including masks, face shields, gloves and disposable booties - primarily to reduce contact with livestock.

“There has been no evidence of human transmission of the H5N1 bird flu virus,” the county’s Deputy Public Health Officer Dr. Thomas Overton told The California Newsroom. “There is no known link or contact between the two confirmed human cases, suggesting only animal to human spread of the virus in California.”

The presence of bird flu at dairies raises questions about how it will impact the industry and its workforce, which accounts for much of the state’s $50 billion a year agricultural revenue.

Tulare County, whose dairy industry dates back to 1860, has been a leading producer of milk in the United States, and is home to 360 dairy farms and half a million dairy cows.

Over 11 million pounds of milk are produced in Tulare County, the most of any other county in the country. That milk also sources major dairy processing facilities located in the county.

California alone produces a quarter of the nation’s milk supply, with most of the production concentrated in seven counties in the San Joaquin Valley.

At latest count, the virus has been reported in 56 dairy herds statewide. According to Anja Raudabaugh, CEO of the industry trade group Western United Dairies, that’s prompted dairies everywhere to reinforce their biosecurity measures to limit contact between animals and humans.

And at dairies where the virus is suspected or confirmed, cows showing symptoms get quarantined in separate pens, and all activities including feed delivery, veterinary visits and milk transportation into refrigerated tankers get physically moved to the outer perimeters of the property.

“This is definitely one of the biggest challenges we've ever faced in California as far as the dairy industry goes,” Raudabaugh. “The amount of stress that it's putting on our farms is significant.”

While the virus isn’t always fatal to cattle, Raudabaugh pointed out that cows that do survive don’t always make a full recovery, and their milk production could remain diminished – especially after such an unusually hot and taxing summer.

“We are seeing an abnormally high rate of cows sent to slaughter,” she said. “Having the cows go down in this manner is not only terrifying to a dairy farmer, but it's very traumatic.”

The latest confirmed detections bring the total number of confirmed human cases of bird flu nationwide to 16, with roughly 230 people tested and nearly 5,000 people monitored after potential exposure as of Friday.

Officials say pasteurized milk and dairy products are safe to consume, since pasteurization is effective at “inactivating” the bird flu virus. But they also add, milk from cows confirmed to be sick is not permitted in the public milk supply.

Avian influenza has been blamed for the deaths of tens of millions of wild and domestic birds worldwide, including millions of poultry birds in the San Joaquin Valley. In other places, it’s killed seals and sea lions, wiped out mink farms and most recently led to the death of tigers in Vietnam, according to the Associated Press. In the U.S., nearly all states have had outbreaks among poultry, while 14 states have seen outbreaks in dairy cows.

The virus only reached people in recent months.

The Centers for Disease Control and Prevention cautions that the risk for humans from bird flu remains low. But specialists like Abraar Karan, who studies infectious diseases at Stanford University, say it’s still something to watch closely.

“We know with influenza viruses there’s a risk of what’s called viral re-assortment, which is essentially when a host gets infected with multiple different strains at once,” Karan told The California Newsroom. “It’s hard to predict what changes could occur.”

Updated: October 6, 2024 at 9:57 PM PDT
This story was updated to reflect a third person was suspected of being infected with bird blu in the Central Valley, though has not been confirmed as of Oct. 6.
Cresencio Rodriguez-Delgado is KVPR's News Director. Prior to joining the station's news department in 2022, he was a reporter for PBS NewsHour and The Fresno Bee.
Kerry Klein is an award-winning reporter whose coverage of public health, air pollution, drinking water access and wildfires in the San Joaquin Valley has been featured on NPR, KQED, Science Friday and Kaiser Health News. Her work has earned numerous regional Edward R. Murrow and Golden Mike Awards and has been recognized by the Association of Health Care Journalists and Society of Environmental Journalists. Her podcast Escape From Mammoth Pool was named a podcast “listeners couldn’t get enough of in 2021” by the radio aggregator NPR One.