San Diego is a stop on the Pacific Flyway. Here’s why that’s impacting the spread of bird flu locally

Researchers say wild bird species in Southern California are contracting a deadlier and more contagious strain of bird flu, causing concern that the virus is more widespread than data shows. 

They say the H5N1 virus is threatening vulnerable species and increasing the chances for mutations capable of transmission between humans. Meanwhile, the Trump administration has fired workers from federal health agencies, sparking concerns over how the cuts may impact the U.S. response to the outbreak.

Having reached all continents except Australia, the flu strain has destroyed poultry flocks, driving headlines for causing widespread egg shortages, but researchers say that endangered birds around the globe are also under threat as more species are contracting the virus.

As migratory birds travel, vulnerable species along the globe’s intercontinental avian flight paths may suffer irreversible impacts on their populations.

San Diego is in the path of the Pacific Flyway, a route that stretches along the Pacific Coast of North and South America. It’s used by over a billion birds every year with some that fly as far south as Patagonia and as far north as Alaska.

“It’s unprecedented, this geographic spread of this particular strain,” said Krysta Rogers, a Fish and Wildlife environmental scientist.

As of Monday, according to the Centers for Disease Control and Prevention, most of the 70 avian flu cases detected among humans in the U.S. have been in California and were transmitted after the virus jumped from birds to mammals, specifically dairy cows. One person has died.

Last week, thousands of health workers lost their jobs following Trump adviser Elon Musk’s slashing of numerous federal agencies and programs, unleashing confusion and protests nationwide. In the process, several U.S. Department of Agriculture workers assigned to the federal avian flu response were accidentally fired, the New York Times reported.

The agency said it’s working to rehire the employees.

Also, the U.S. Centers for Disease Control and Prevention posted and deleted data from their website regarding bird flu transmission between humans and domestic cats, leading to more confusion and demands for current critical information.

Meanwhile in California, unionized workers at the state’s only official bird flu testing facility, a federally funded lab at U.C. Davis, say they are overworked and understaffed.

The shake up on both the federal and state levels has caused dismay for specialists.

Responding to the virus is a collaborative effort, said Mikah Curtis, who oversees the intake of injured and potentially infected animals at the San Diego Humane Society’s Project Wildlife.

Curtis described the various facets of local and federal response, from research to testing to dissemination of accurate information, as a chain held together by several leanly staffed organizations.

“If one of those chain links is not working well, the whole thing breaks,” Curtis said.

Viral highway

Initially, when the highly pathogenic avian flu strain was detected in 2022, it primarily impacted Northern California. But scientists say that they have been tracing its steady movement south following migration paths.

In San Diego there have been 22 unconfirmed detections of the virus in wild birds collected between October and January, as well as a detection in Imperial County. But the number of infected wild birds is likely more, Rogers said, noting that only some birds are tested, and there may be many unknown cases in remote and hard to reach areas.

“As you can imagine, there’s a lot of virus activity right now, and wildlife are kind of at the bottom of that priority list. We have many preliminary detections that aren’t yet confirmed by USDA,” Rogers said.

Birds can contract the virus if they’re near each other, through contact with feces or by ingesting infected meat. Some birds can carry the virus without manifesting symptoms, making them ideal carriers, like certain species of migrating waterfowl. For others the virus is swift and deadly. Over a period of weeks, the virus killed off 40% of Peruvian Pelicans in 2023.

In San Diego, infected species include the endangered Ridgeway’s Rail, as well as other wild birds, including the American White pelican and Wigeon, the California and Western Gull, as well as birds of prey such as the Great Horned Owl, Peregrine Falcon, Turkey Vulture and the Common Raven.

San Diego’s estuaries are a crucial resource for birds stopping to “refuel” on the Pacific Flyway, a migration path that spans North and South America along the Pacific coast from tip to tip. And space is limited. 

“We’ve lost over 90% of our coastal wetlands in California,” said Chris Peregrin, a California State Parks employee who manages the Tijuana River National Estuarine Research Reserve. “And so you have animals that are in these small islands of natural open space throughout an area of highly developed urbanized environment.”

That also means that migratory birds can carry the virus and introduce it to more vulnerable bird populations that share protected areas. Sea birds, which often nest in closer proximity to one another and produce less offspring are particularly vulnerable, said Rebecca Duerr, the research director of the International Bird Rescue.

Between its San Francisco and Los Angeles wildlife centers, Duerr’s organization helps rehabilitate birds in California and has been aiding the San Diego Humane Society’s Project Wildlife with animal intakes during the influx of the flu.

Both organizations interface with sick birds. If they suspect a bird may have the flu, protocol is to euthanize the animal, swab for flu and send the test to the state’s testing lab at U.C. Davis.

“One of the tasks of the wildlife centers in California is to essentially sort out the treatable from the untreatable,” Duerr said. “There are a lot of other things that can cause neurologic signs in wild birds, like head trauma or harmful algal blooms or toxicities, but it’s really difficult to even attempt to try to treat those animals now, since there’s this nasty contagious disease.”

An uncertain future

The increase in avian flu infections among wild birds means that the virus has more opportunities to infect domestic bird populations. It also means more opportunities for the virus to mutate, increasing the possibilities of a strain that could have a stronger impact on humans, or that could jump between humans.

Last week San Diego County announced its first suspected case of bird flu in a house cat in East County. The cat became sick and died in mid January, officials suspect it may have contracted the flu from raw food. Curtis from Project Wildlife also says that cats can also contract it from hunting wild birds while on the loose.

Researchers rely on testing and studies to trace how the virus is developing. For this reason, the firings of federal employees at health agencies and lack of clarity on what the future might hold for agencies such as the federal Centers for Disease Control and Prevention, or the CDC, have made some frontline specialists uneasy.

Some of the firings reportedly affected employees from the National Animal Health Laboratory Network, a USDA program for monitoring animal disease outbreaks. The agriculture department has said it would try to rehire the employees. 

Curtis from Project Wildlife says that consistency and access to accurate information through government channels are key to protecting public health.

The U.S. Department of Agriculture did not answer inewsource questions about whether its avian flu response has been affected by recent cuts. The CDC referred inewsource to the Department of Health and Human Services, which declined to answer questions.

Meanwhile at U.C. Davis, union representatives for lab workers at the federally funded lab that runs bird flu tests say that lab has been understaffed, creating conditions that threaten the lab’s ability to respond to the avian flu outbreak. Last week, the workers held a three-day strike to demand wage increases and other benefits from their employer, a California public university.

The lab is part of the National Animal Health Laboratory Network, though the strike is unrelated to the federal cuts.

Amy Fletcher, a member of UPTE’s leadership, said that workers at the lab brought to her attention that there were only two diagnosticians left in a lab normally run by seven individuals, and that they were concerned of making errors due to being overworked.

“We could have false positives, which means we’re unnecessarily killing thousands of birds, or we have some false negatives,” Fletcher said.

Before the strike, a spokesperson for U.C. Davis said the university and its partners, “have successfully met and continue to meet the demand for diagnostic testing to protect animal and human safety” and were prepared to continue that work during a strike. “Our lab continues to fulfill its mission of safeguarding public health with rapid and reliable diagnoses for animal diseases through the hard work of our team,” the spokesperson said.

Curtis from Project Wildlife is concerned that the partisan issues on the federal and state level are a distraction from a problem that could become even more deadly, especially if it’s not properly monitored or if efforts are underinvested.

“We saw the handling of COVID,” Curtis said, adding that some decisions were made that put the public at risk. “I really hope that that does not happen with something like this, because this could be a much deadlier, bigger scale issue.”