A new and growing threat is facing America’s largest bird, California condors, a famed species that has been slowly recovering from the brink of extinction in recent decades.

A highly contagious strain of avian influenza has killed at least 18 of the massive birds around the Grand Canyon in Arizona over the past month. And now California biologists are scrambling to address what could be a catastrophic setback if condors in Big Sur and other parts of the state become infected.

“The disease has moved so quickly, and a vaccine development has not,” said Kelly Sorenson, executive director of the Ventana Wildlife Society, a non-profit group that has released condors into the wilds around Big Sur and San Simeon since 1997. “We are in a very tough spot.”

“We are preparing for a worst-case scenario,” he added. “It has the potential to be devastating to the population.”

As of Tuesday, officials have recorded 363 cases of wild birds in California being infected by avian influenza — more than in any other state except Minnesota and Florida, which had 566 and 415.

In California, the disease has also killed bald eagles and golden eagles, turkey vultures, ducks, geese, ravens, gulls, sanderlings, grebes and other birds, including in most Bay Area counties. So far, no condors have been found infected in the Golden State. Avian influenza had not been known to kill condors until the first bird in the Grand Canyon died on March 20.

In the worst-case scenario, if the disease spreads widely across California, scientists say they could begin capturing wild condors to protect them until a vaccine is developed.

“That’s not really a great option,” Sorenson said. “It’s not something they would enjoy, to put it lightly. But it’s better than losing a large number of birds. We are trying to prepare for all scenarios.”

Sorenson’s organization this week purchased 10 large steel quarantine pens, each 12 feet long, so they can care for condors, whose wingspans can stretch 9 feet.

The pens are located on land donated by the Monterey County SPCA along Highway 68 between Salinas and Monterey.

Condors once ranged from British Columbia to Mexico. But because of habitat loss, hunting and lead poisoning, the majestic birds reached a low of just 22 nationwide by the early 1980s.

In a desperate gamble to stave off extinction, federal biologists captured all the remaining wild condors in 1987 and began breeding them in the Los Angeles Zoo, San Diego Zoo and other facilities. The birds’ offspring have been gradually released back to the wild in Big Sur, near the Grand Canyon, at Pinnacles National Park, and in Kern County, in Baja, Mexico, and most recently near Redwood National Park. The first condors in modern times to be born in the wild hatched in 2007, and today there are 561 California condors, with 347 in the wild.

According to the U.S. Fish and Wildlife Service, on March 9, employees of the Peregrine Fund, a non-profit group that manages the flock of 116 wild condors that fly in the Grand Canyon and parts of Utah, saw a female condor that appeared to be sick.

They thought it had lead poisoning, a common cause of death among condors who eat deer and other animals that have been shot by hunters and ranchers, ingesting bullet fragments.

On March 20, they found the bird dead below her nest. Tests confirmed the animal died from Highly Pathogenic Avian Influenza, a type of “bird flu” that has killed millions of chickens across the world and wild birds.

As of Wednesday, 18 condors from the Grand Canyon area have died, with 6 confirmed from the disease and the other 12 suspected to have died from it. Another five are in veterinary care and undergoing testing for the disease, which veterinarians and biologists call “HPAI.”

Scientists think the condors were exposed through contact with wild birds, potentially birds migrating from South America.

A young California condor lands at the Ventana Wildlife Society's condor sanctuary in Big Sur, Calif., Friday, Nov. 18, 2022. (Karl Mondon/Bay Area News Group)
A young California condor lands at the Ventana Wildlife Society’s condor sanctuary in Big Sur, Calif., Friday, Nov. 18, 2022. (Karl Mondon/Bay Area News Group) 

The disease’s particular strain, known as H5N1, is considered low risk as a human health concern, according to the Centers for Disease Control. But it is highly contagious in wildlife and can spread quickly by bird-to-bird contact, contamination with birds’ fecal material, and through exposed clothing, shoes and vehicles.

So far, the disease has killed nearly 1 in 6 of the Arizona-Utah population, a group that has been painstakingly recovered over many years.

The 18 deaths in the past three weeks are more than the total number of wild condors that died in each of the past four years from lead poisoning in all locations across Western North America where they have been released.

“It’s scary,” said Ashleigh Blackford, condor program director for the U.S. Fish and Wildlife Service. “This is a program where people have invested a lot of time in this recovery effort. This is a monumental blow in short amount of time. You can go backward so quickly.”

Blackford said scientists are still learning about the disease, how it spreads, and how to care for condors who might be exposed.

“This is like the first two weeks when COVID first came out,” she said. “Things are happening rapidly. We don’t have enough data, but we are collecting it rapidly.”

Biologists who deal with condors have been wearing protective coveralls, washing their shoes, and taking steps such as not leaving out dead animals for them to feed on so they don’t congregate.

The Central California population of 94 wild condors is still recovering from the Dolan Fire in Big Sur in 2020, which killed 12 of the endangered birds.

It was unclear Thursday, however, what steps Pinnacles National Park in San Benito County is taking to prepare for the spread of the disease in its flock of 29 condors. Park officials referred calls to the National Park Service media office in Denver, and spokesman Naaman Horn said he would not make park scientists available for interviews Thursday, saying all national parks needed to have a coordinated message to the public.

But Sorenson expressed concern.

“Lead poisoning has been the number one threat to the recovery of the species,” he said. “But this is quite worrisome because condors are highly social and this disease is very contagious.”