A lack of wastewater testing is blinding the Central Valley to its bird flu problem
- California’s Central Valley is where many of the people most vulnerable to bird flu live and work, and where the majority of cases in humans have been found.
- Wastewater surveillance should be a key public health tool to understand how the virus is spreading — but experts say the region’s testing of wastewater is not up to par.
As the H5N1 bird flu virus continues to rip throughout California’s dairy herds and commercial poultry flocks, a Central Valley state official is raising concern about the lack of wastewater surveillance in the region.
State Sen. Melissa Hurtado (D-Sanger) has been frustrated by what she says are gaps in tracking the bird flu’s spread in the Central Valley, where many of the state’s most vulnerable people — dairy and poultry workers — live and work.
“If you’re tracking disease that spreads from animal to human, you want to be looking at rural areas, like the county of Tulare where there are more cows than there are people — yet there’s no testing of wastewater anywhere south of Fresno in the valley,” Hurtado said.
As of Dec. 30, 37 people in California have tested positive for H5N1; all but one was a dairy worker. In addition, more than two-thirds of the state’s dairy herds — 697 — have been infected, as well as 93 commercial or backyard poultry flocks, accounting for nearly 22 million birds.
On Dec. 18, Gov. Gavin Newsom declared a state of emergency after the virus jumped from the state’s Central Valley dairy herds into Southern California dairy cattle, despite quarantine restrictions designed to stop the spread.
The virus, which is also moving in migrating birds and wildlife populations, has been detected in wastewater sites around the state, including in Los Angeles, San Francisco and San Jose.
However, sampling is sparse in the Central Valley, where the majority of human cases have been reported and the risk is high. Indeed, wastewater sampling for bird flu is nonexistent in some of the counties most at risk, including Tulare and Kings.
Why current testing is not good enough
Sampling wastewater helps public health officials track a virus’ spread. It has been a tactic officials employed during the COVID-19 pandemic in order to monitor the coronavirus spread. In California, officials used wastewater to predict waves of infection and just how much the virus was circulating among populations.
In California, health officials say they are monitoring 78 sites in 36 counties for a range of viruses; in all but two sites they say they are looking for bird flu.
In an email to The Times, state officials said the state’s Cal-SuWers Network is monitoring six sites in the Central Valley, including in Kern, Merced, Stanislaus and San Joaquin counties.
According to the Centers for Disease Control and Prevention, the most recent sample from Kern County was submitted Dec. 7, and it was positive for the virus.
It’s a major blind spot in the state’s surveillance system, state officials acknowledge, yet note it’s one they have little control over.
“Availability of wastewater monitoring at a site … requires utility participation, which is voluntary,” said Ali Bay, spokeswoman for the state agency. “Competing priorities and resource constraints can reduce a [utility’s] capacity to participate.”
Tulare County and Kings County lead the state with the most human cases, according to the numbers each county has released.
Laura Flores, a spokesperson for the Tulare County public health department, said the county’s independent wastewater treatment plants have chosen not to participate in the state’s surveillance program. Tulare has 18 reported cases, the most of any county and nearly half the state’s total.
Everardo Legaspi, deputy director for Kings County public health department, told The Times they have had four confirmed cases. The county has been unable to participate in the state’s wastewater surveillance project since October because of staffing shortages, he added, but the county is working to begin wastewater collection and expand it to other sites in the county.
For months, experts have been concerned that public health authorities have been lethargic in their response to the burgeoning pandemic, and that public safety has taken a back seat to agricultural interests. It was only last month that the U.S. Department of Agriculture began a program to test for the virus in the nation’s raw milk supply — roughly a year after experts believe the virus spilled into cattle, and after more than 900 dairy herds and 60 people were infected.
“I do think that people are continually minimizing this outbreak and this virus,” said Rick Bright, a virologist and the former head of the U.S. Biomedical Advanced Research and Development Authority. “Our government officials are not doing the thorough investigation they should be doing.”
Even after the USDA’s announcement about the new bulk milk testing program, only 13 states are being included in the initial rollout; many, including California, Colorado and Michigan, were already testing their milk.
And the incoming Trump administration has threatened to pull the U.S. out of the World Health Organization, a move that would further blind the U.S. and the rest of the world to the virus’ movements. Although the Biden administration announced Thursday that it was committing an additional $306 million to ward off a potential outbreak of bird flu in humans — funds that would be distributed before he leaves office later this month.
“I don’t think that the right questions are being asked to have an understanding of this bird flu,” Hurtado said. “In large part it’s because there’s just a lack of guidance coming from the feds.”
What we could learn from bird flu surveillance if we were doing it right
To be sure, finding bird flu in wastewater does not mean there is a human outbreak of the virus.
Unlike COVID-19, mpox or seasonal influenza — which when found in wastewater indicate human infections — positive samples of bird flu could be from a variety of sources, including pasteurized milk. That’s because the method used to sample for bird flu in wastewater looks for markers of the virus, not the whole virus.
That means the tests could be picking up inactivated fragments of the virus, like those found in commercial pasteurized milk.
“I don’t think we really know what it means,” said Richard Webby, director of the World Health Organization’s Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds. ”How much milk gets poured down the drain in an urban area? We know we can get high… loads in supermarket milk. I actually have no clue what supermarkets do with expired milk.”
It’s also possible it’s coming from raw milk or raw meat. Or even waste products from wild birds and mammals, in which the virus is also currently circulating.
Since the beginning of the outbreak, California officials have found the virus in wild birds such as rock pigeons, white-faced ibis, and turkey vultures, as well as wild mammals including mountain lions, raccoons and skunks.
San Bernardino resident Joseph Journell says he lost two beloved cats after they drank raw milk contaminated with bird flu and is threatening to sue Raw Farm owner Mark McAfee.
In addition, it’s possible people are shedding inactivated virus in their feces, said Alexandra Boehm, professor of civil and environmental engineering at Stanford University and principal investigator and program director for WastewaterSCAN.
The fight to improve the system
Irrespective of what the samples are showing, they provide evidence that the virus is circulating somewhere in the environment.
And the fact that health and water utility officials in certain regions of the state are willfully not looking for it is another example of the government’s failure to contain the disease and keep track of its spread, said Bright.
“The virus is evolving quickly. … Without full participation in surveillance and testing programs, coupled with full and timely transparency, we will always be behind the virus,” said Bright. “Our ability to get in front of it will be hampered without full collaboration and cooperation at federal, state, local and community levels.”
When, where and how the H5N1 bird flu virus may evolve and its capacity to spark a pandemic is hard to predict — in part, some researchers say, because of federal restrictions on gain-of-function research.
For Hurtado, the situation is also personal.
She said her father and her niece, who live in the Central Valley, displayed bird flu symptoms earlier this year, but no testing was available to confirm her suspicions.
Her father contracted a virus that nearly killed him and involved severe muscle and body aches, a symptom of bird flu. Her 7-year-old niece, who lives in Sanger, a town with a large poultry processing plant, recently had a rare autoimmune response to a virus, and she had red, swollen eyes, a symptom of the H5N1 virus. Her doctors don’t know what triggered the reaction.
Despite showing symptoms, she said, neither was tested for bird flu — but she suspects they had it. Dairy farmers, workers and family members have also told The Times that they believe the state’s reported numbers are likely an undercount, as some workers may not report being sick for fear of losing work.
“I don’t have the science or the information to back it up, but my heart tells me both my father and my niece got the bird flu,” she said. “Both were impacted by severe illness by some unknown virus.”
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The personal experience has driven her to push the state for answers on tracking the virus’ spread. She has asked the state’s health department about the lack of Central Valley testing but she said she hasn’t gotten a clear response.
Hurtado has also pushed for an increase in testing in high-risk communities. Despite some testing for individuals at risk, including dairy and poultry workers, the state doesn’t offer a comprehensive way to test heavily agricultural communities.
Hurtado, whose district includes a large swath of the Central Valley, said she intends to propose legislation that would expand the state’s wastewater surveillance program to include sites in underserved and high-risk communities in rural areas. The legislation would also develop criteria for identifying high-priority sites based on health risks, population density and socioeconomic factors.
Hurtado worries about communities like Sanger, her hometown. There is a poultry processing plant, one of the largest employers in the city and county, that has been hit hard by bird flu.
Since the end of October, a dozen commercial poultry operations in Fresno County have been hit by the virus, resulting in the culling of more than 1.5 million birds.
She has heard stories of workers losing hours of work as animals have gotten sick and poultry farms have been entirely depopulated. The price of eggs also has risen as a result of the outbreak.
“I think we could’ve done a lot more a lot earlier,” she said. “But we’re here, and we’ve got to be able to improve upon where we’ve failed.”
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