A swarm of flies surrounded a heap of around a dozen lifeless cows at a dairy farm in California.

This disturbing sight, captured in a viral video earlier in October, has prompted serious concerns. The cows were affected by bird flu, a virus that has spread among cattle in at least 14 states and has quickly become prevalent in California’s Central Valley, which is the leading area for dairy production in the country.

Representatives from the industry and state officials confirmed that the grim scene was filmed outside a farm that had experienced a virus outbreak. The region faced extremely high temperatures, which officials suspect may have contributed to the mortality of the cows.

This footage highlights the severe consequence of the fast-moving bird flu that has been affecting dairies across the U.S. since it transferred from wild birds in Texas nearly a year ago to large-scale dairy operations in California. The virus has reportedly infected dozens of farmworkers, including 15 dairy employees in California as of Thursday morning.

Fortunately, bird flu has not significantly affected the country’s dairy supply. Pasteurized milk is safe for consumption as this process eliminates harmful pathogens. However, officials are concerned about the broader impacts on farmers and workers. Federal support has been extended to farmers facing losses of livestock or products.

Authorities maintain that the general risk to the public is low. However, the threat is greater for farmworkers, many of whom are Latino immigrants and might not have full work authorization. These workers often come into direct contact with infected livestock, with 30 cases of bird flu reported among them across the U.S. by Thursday.

“It’s not currently a public health issue. However, it has the potential to become one,” explained Bethany Alcauter, the director of research and public health programs at the National Center for Farmworker Health, a nonprofit involved in the federal bird flu response. “At this moment, the primary concern is the health of the workers.”

Is California becoming the new center for bird flu?

California identified its first infected cow in August and its first human case of the disease this month. So far, 137 herds have reported infections.

“We have been monitoring its approach for quite a while,” noted Anja Raudabaugh, CEO of Western United Dairies, an organization representing California dairy farmers, as stated to YSL News. “Our enhanced biosecurity efforts have worked to some extent, but they eventually failed. Now we are witnessing substantial cow-to-cow transmission, presenting a major hurdle for our dairy farmers in California.”

Data from the U.S. Department of Agriculture indicates that over 330 dairy herds across 14 states have reported infections, with California accounting for more than a third of those cases.

“Do we, as in California and the U.S., want to be the next epicenter for a pandemic?” questioned Dr. Gail Hansen, a former public health veterinarian in Kansas, while speaking to YSL News. “I certainly don’t. I don’t wish to sound too alarming, but it is a real possibility.”

Deceased cows in the Central Valley

In early October, Dr. Crystal Heath, a veterinarian from California and founder of the animal welfare organization Our Honor, recorded a video showing dead cows in Tulare County, the area with the highest dairy production in California. She noted that there were no visible precautions taken to restrict access to the infected carcasses.

According to the California Department of Food and Agriculture (CDFA), dead cows infected with bird flu need to be isolated from their herds. The video illustrated this separation, but the animals must be kept on private property before being moved for “disposal” and should never be buried underground, the department clarified.

Raudabaugh, representing the farm shown in the clip, stated that proper procedures were followed for separating the carcasses. She emphasized that the deceased cows cannot be processed for meat. Instead, they are sent for “rendering,” a process where they are incinerated and repurposed for products like tallow or leather.

Raudabaugh explained that when the video was taken, the rendering truck scheduled to collect the deceased cows had been delayed for several days.

While the bird flu can cause death in cows, the American Veterinary Medical Association considers the overall mortality rate to be relatively low, around 2%.

However, Raudabaugh’s dairy council estimates that mortality rates from bird flu might be closer to 10 to 15%. Additionally, the area has faced a late-season heatwave, complicating the determination of whether temperatures contributed to the increased fatalities.

Dr. K. Fred Gingrich II, the executive director of the American Association of Bovine Practitioners, an organization that represents veterinarians treating cows, noted there haven’t been significant fluctuations in the mortality rates attributed to bird flu.

He views the dead cows shown in the video as an isolated case but acknowledges that it highlights the importance of biosecurity measures in curbing the virus’s transmission on farms. He pointed out that rendering trucks do not enter farms to avoid exposing herds to diseases; instead, they collect dead cows at the nearest roadway. This precaution safeguards cattle but can lead to negative media attention for farms from animal rights activists, he remarked.

During a press conference on Thursday, Dr. Eric Deeble, a senior official from the USDA, stated that there is no indication of variations in the bird flu affecting cows in California as compared to other states. He suggested that the reported increase in cattle mortality in the Central Valley might be linked to environmental conditions such as extreme heat, agricultural practices, and the high density of animal populations.

Dr. Elisha Frye, an associate professor from Cornell University, highlighted that the typical breed of dairy cows in the U.S. is the black and white Holstein, which hails from cooler regions in northern Europe.

These cows can weigh over 1,500 pounds and are capable of producing around 100 pounds of milk daily, comparable to a marathon run for a person. She added that the daily exertion makes cows more susceptible to heat stress, especially when they are unwell.

Transmission of Bird Flu in Cows

The method of bird flu transmission among cows is still not well understood.

Initially, it was thought that movement of cows between farms and across state lines—common in the dairy industry—was a key factor in spreading the virus. In response, the USDA mandated testing of the milk from lactating cows before they could be transported across state borders. However, bird flu outbreaks continued to emerge across the nation. According to the Los Angeles Times, the virus was likely brought to California through the movement of cattle.

The USDA noted that the virus spreads via contact with contaminated items such as milking equipment, clothing, vehicles, and farm tools that have been near infected animals. This allows bird flu to circulate within herds.

The USDA strongly recommended that farmers follow guidelines designed to reduce risks. This includes minimizing the movement of people, cattle, and equipment between farms.

Gingrich noted the challenges of managing this issue on large farms in the Central Valley, where farming is a deep-seated part of the community.

“We lack a clear understanding of how many dairies are impacted,” Gingrich told YSL News. “Producers are often reluctant to disclose this information unless there is a state mandate.”

If he were a dairy farmer in an affected area, Gingrich said he would conduct bulk milk testing, which is required on California farms that have infected herds and those in proximity.

Testing milk samples can detect the virus before cows present any symptoms. This proactive approach would enable farmers to swiftly take preventive measures, alert veterinarians, and inform neighboring farms of any infections. Gingrich called for enhanced national surveillance through bulk milk testing.

Human Infection of Bird Flu

Researchers are still investigating how bird flu spreads to humans. Almost all of the 31 reported cases this year occurred among poultry and dairy farm workers, and officials anticipate more cases. Importantly, there is currently no evidence of human-to-human transmission.

At dairy farms, transmission to workers seems to occur through close interaction with infected animals, particularly when handling udders and raw milk, where the virus is most prevalent. Workers face infection risks if they come into contact with contaminated surfaces or if milk splashes and they then touch their face.

Workers who have contracted the virus reported mild symptoms, including redness in the eyes, and have generally recovered quickly, according to state and federal health officials.

The rising number of confirmed cases likely indicates increased awareness and testing, noted Dr. Dean Blumberg, chief of pediatric infectious diseases at the University of California, Davis, Health. There appears to be no change in the transmission methods from animals to humans.

No instances of human infection with bird flu have been reported in Fresno County, located in the Central Valley. However, Dr. Rois Vohra, the county’s interim health officer, remains cautious.

“We have been fortunate so far,” said Vohra, who is also an emergency medicine professor at the University of California, San Francisco. “These cases have been quite mild, and individuals have recovered swiftly. Yet, we must remain vigilant.”

Measures to Safeguard Workers

Dr. Vohra stated that the protective measures adapted during the COVID-19 pandemic can be effectively applied to combat bird flu. These strategies include utilizing personal protective equipment. While N95 respirators provide a form of protection, they can be challenging to wear comfortably in the hot conditions typical of the Central Valley. Nevertheless, he emphasized the necessity of goggles and face shields.

Seasonal flu vaccinations are another precautionary measure. Although these vaccines don’t guard against bird flu, officials worry that simultaneous infections from both viruses could lead to a more severe or contagious strain of bird flu.

Labor advocates express concern about whether adequate resources are being allocated to ensure the safety of dairy workers, who play a crucial role in controlling the spread of bird flu in the U.S.

“There seems to be an abundance of resources directed toward protecting business interests,” commented Elizabeth Strater, director of strategic campaigns for the United Farm Workers, a union that has long been active in California’s Central Valley (though not representing local dairy workers). “Yet, very few of those resources are being effectively utilized to protect the health of the workers who are known to be at high risk.”