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California - Avian flu in mammals and livestock 2025-2026

October 29, 2025: H5N1 Bird Flu in Livestock Updates

​SACRAMENTO, CA — California currently has 13 dairy herds under Quarantine for H5N1 Influenza infection, with six (6) of those herds being re-quarantines of previously infected herds. The re-quarantined herds were new detections on diaries that were infected previously that had had their CDFA quarantine lifted after 3 negative whole herd tests via weekly bulk tank milk samples. These six (6) farms have been shown to have sufficient virus present to be placed back under State Quarantine at this time.

All dairies in the state continue to be under regular surveillance as part of sustained monitoring of the virus in California.

https://www.cdfa.ca.gov/AHFSS/Animal_Health/HPAI.html
 
previous post #81:
The re-quarantined herds were new detections on diaries that were infected previously that had had their CDFA quarantine lifted after 3 negative whole herd tests via weekly bulk tank milk samples. These six (6) farms have been shown to have sufficient virus present to be placed back under State Quarantine at this time.

As of 10/31/25 @ 7:30am EST neither the 13 herds, or the 6 re-quarantined herds are listed at USDA APHIS webssite.

Screenshot 2025-10-31 at 7.46.13 AM.png
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Screenshot 2025-10-31 at 7.40.56 AM.png


https://www.aphis.usda.gov/livestoc...pai-detections/hpai-confirmed-cases-livestock

 
Media
California agriculture dept. is hiding bird flu information, legal aid group alleges in lawsuit
  • Susanne Rust Los Angeles Times
  • Nov 7, 2025 Updated 12 hrs ago


LOS ANGELES — A rural legal aid group is suing the California Department of Food and Agriculture for refusing to disclose the locations of dairies infected with H5N1 bird flu.

More than half of the 70 confirmed human cases of H5N1 bird flu infection in the United States in the last year and a half have been in California dairy workers.

California Rural Legal Assistance, a nonprofit that provides free civil legal services to low-income rural residents, together with the First Amendment Coalition, says the California agriculture department is withholding information that could protect the public and allow front-line responders, such as health clinics and labor groups, to assist farm workers and others at risk of infection.

"As a matter of first principle, the California Constitution and the California Public Records Act enshrine the strong right of the public to inspect the conduct of its public officials and to ensure that they are basically executing the duties that are given to them," said David Cremins, an attorney with the rural legal group. The suit was filed Monday in Sacramento County Superior Court.

A spokesman for the state's agriculture agency said he could not provide comment "because the matter is in litigation."

Anja Raudabaugh, CEO of Western United Dairies — California's largest dairy trade group — also declined to comment.

-snip-

In December 2024, Gov. Gavin Newsom declared a state of emergency in response to H5N1 and said he wanted to make sure that "Californians have access to accurate, up-to-date information" about the disease.

The state did release information on outbreaks at poultry facilities and in wild animals at the county level. But it did not do so for dairy outbreaks.

Agriculture officials described the infected cattle only as being in "the Central Valley" — an area encompassing roughly 20,000 square miles — or Southern California — a roughly 56,000 square mile area.

More than 770 dairies in California have been infected since the outbreak began in 2024.

Such vague information is "completely useless in terms of trying to figure out how the flu is spreading around," said Angela Rasmussen, a virologist at the University of Saskatchewan's Vaccine and Infectious Disease Organization in Canada.

"It's a bit mystifying why that information isn't clear and transparent," she said. "I mean, when you're dealing with an outbreak that has major implications in terms of both people's livelihoods and in terms of the nation's food supply, to not be more transparent about that, I think is actually really harmful in the long run, because it's like, what are you guys doing? Like, why are you keeping this a secret?"

Cremins, the attorney, said it's possible infections among dairy workers could have been avoided had location information been shared, because groups like his and "other members of the public" could have targeted "outreach and education to at-risk workers and communities."

The plaintiffs also allege in their filing that the agriculture department's "refusal to disclose the locations of H5N1 outbreaks ... perpetuated a stark and unjustifiable information asymmetry: CDFA (the ag agency) and dairy producers know where and when bird flu outbreaks are occurring; CRLA (the legal organization), dairy workers, and the broader public do not."

Other states, including Michigan, Arizona and Nevada, reported outbreaks at the county level.

The plaintiffs are seeking disclosure of quarantine records, a declaration from a judge that the agriculture agency violated the state's open record laws, and — should they succeed — payment of attorney's fees.

https://hanfordsentinel.com/busines...cle_6434fdf2-f4cb-4ec7-b334-bd51250a005f.html


 
CDFA
December 31, 2025: H5N1 Bird Flu in Livestock Updates



SACRAMENTO, CA — California currently has four (4) dairy herds under quarantine for H5N1 influenza infection, including one (1) herd that was re-quarantined following a new detection on a previously cleared premises. The re-quarantined herd is located on a dairy that was previously infected and had its CDFA quarantine lifted after three consecutive negative whole-herd tests using weekly bulk tank milk samples.

Progress in California
  • Only four dairies remain under quarantine statewide, reflecting continued progress in enhanced mitigation measures.
  • All dairies in California remain under ongoing surveillance as part of sustained monitoring for H5N1.
  • CDFA lifted the statewide ban on poultry and dairy cattle exhibitions at fairs and shows, effective December 19, 2025.
National Detections

This nationwide outbreak of H5N1 Bird Flu began in poultry in 2022 and was first detected in US dairy cattle in March 2024. All national detections in cattle can be found on the USDA website at: HPAI Confirmed Cases in Livestock | Animal and Plant Health Inspection Service (usda.gov). All national detections in poultry can be found on the USDA website at: Confirmations of Highly Pathogenic Avian Influenza in Commercial and Backyard Flocks | Animal and Plant Health Inspection Service (usda.gov)

Note: The USDA website reports new (first time detections) in dairies; it does not capture when a herd is cleared, ongoing cases, or reinfections on premises that had previous detections.

continued: https://www.cdfa.ca.gov/AHFSS/Animal_Health/HPAI.html
 
For Immediate Release: Wednesday, February 25, 2026

First Cases of Highly Pathogenic Avian Influenza in Northern Elephant Seals Confirmed in California

Cases at Año Nuevo State Park Mark State’s First Detectionof the Disease in a Marine Mammal


For six decades, researchers at UC Santa Cruz have been closely monitoring the colony, providing a unique opportunity to investigate the outbreak in individually identifiable seals and understand the potential near and long-term impacts to population health.

UC Davis scientists have been testing samples from marine birds and mammals at the park and other regions along the coast since 2024. The NSF Center for Pandemic Insights at UC Davis and UC Santa Cruz have been working together to increase surveillance at this site over the past two months in anticipation of a possible outbreak in seals.

The scientific team is now working closely with NOAA Fisheries, the California Department of Fish and Wildlife and the West Coast Marine Mammal Stranding Network to continue to monitor marine mammals along the coast.

“We are cautiously optimistic, as most of the adult females had already departed the beach for their routine migrations before the outbreak began, and most seals on the colony seem healthy,” Beltran said.

People and pets should keep distance
While risk of infection to the general public is low, HPAI can spread between animals and people. Do not touch live or dead seals or allow pets to approach them. This helps protect people and pets and also gives sick animals space.

If you encounter a sick, injured or dead marine mammal in California, Oregon or Washington, call the NOAA Fisheries West Coast Region Stranding Hotline: (866) 767-6114. Do not attempt to move sick wild animals, as this can spread disease and cause stress or harm to the animal.

Looking back and ahead
The H5N1 virus was discovered in 1996 in Southeast China on a domestic goose farm. It was transmitted within the poultry industry for several years, during which it spilled over into wild birds and humans and then spread to Europe, the Middle East, Africa and later to North America, South America and, in early 2024, to Antarctica.

The current outbreak of HPAI in North America was first detected in early winter 2021 in Newfoundland and Labrador, Canada. It has now been confirmed in nearly all U.S. states and Canadian provinces, in commercial poultry, backyard flocks, many species of wild birds, and several species of mammals, including humans.

Two previous HPAI outbreaks in U.S. marine mammals occurred in Maine in 2022 and Washington in 2023. These events were caused by direct spillover of virus from infected birds to seals.

Sustained wildlife surveillance and monitoring is a critical but ongoing challenge for preventing and detecting outbreaks globally. The NSF Center for Pandemic Insights at UC Davis, with collaborators at 12 other institutions, including The Marine Mammal Center and UC Santa Cruz, has been working to develop innovative technologies and methodologies – from chemical sensors to drones – to be able to scale up HPAI surveillance, especially in populations that are less monitored and often harder to access.

The team will generate weekly updates and continue to closely monitor and test samples collected from sick animals, conduct drone surveys, and ensure systematic observations.

More information about this outbreak, including future updates, will be available at the Institute for Pandemic Insights website.

https://www.parks.ca.gov/NewsRelease/1485

 
First cases of highly pathogenic avian influenza in northern elephant seals confirmed in California

​The outbreak marks the first cases of HPAI H5N1 in marine mammals in California and the first detection in northern elephant seals.
February 25, 2026

Seven weaned elephant seal pups in California’s Año Nuevo State Park tested positive for highly pathogenic avian influenza (HPAI) H5N1, the U.S. Department of Agriculture’s National Veterinary Services Laboratory confirmed Tuesday evening.

The outbreak marks the first cases of HPAI H5N1 in marine mammals in California and the first detection in northern elephant seals. The disease decimated populations of a related species, southern elephant seals, in Argentina in 2023.

“This is exceptionally rapid detection of an outbreak in free-ranging marine mammals,” said Professor Christine Johnson, director of the Institute for Pandemic Insights at the University of California, Davis’ Weill School of Veterinary Medicine. “We have most likely identified the very first cases here because of coordinated teams that have been on high alert with active surveillance for this disease for some time.”

Scientists at UC Santa Cruz and UC Davis increased disease surveillance of this population in recent years due to concerns about avian influenza’s spread throughout North and South America.

“Given the catastrophic impacts observed in related species, we were concerned about the possibility of the virus infecting northern elephant seals for the first time, so we ramped up monitoring to detect any early signs of abnormalities,” said Roxanne Beltran, a professor in Ecology and Evolutionary Biology at UC Santa Cruz. Beltran’s lab leads UC Santa Cruz’s northern elephant seal research program at Año Nuevo.

On Feb. 19 and 20, Beltran’s team noticed seals at Año Nuevo Reserve with abnormal respiratory and neurological signs, including weakness and tremors. They collected samples from sick and dead elephant seals and took them to UC Davis for testing at the California Animal Health and Food Safety Laboratory System. Initial screening revealed the samples were positive for avian influenza, which the USDA’s NVSL lab now confirms is HPAI H5N1.

Monitoring the colony

Año Nuevo State Park, just north of Santa Cruz, is home to an elephant seal colony with approximately 5,000 seals during the winter breeding season. About 1,350 seals were present on the beach when the outbreak began. California State Parks has temporarily closed public access to seal viewing areas and cancelled its popular guided elephant seal tours for the remainder of the season while officials investigate the wildlife health threat.

For six decades, researchers at UC Santa Cruz have been closely monitoring the colony, providing a unique opportunity to investigate the outbreak in individually identifiable seals and understand the potential near and long-term impacts to population health.

UC Davis scientists have been testing samples from marine birds and mammals at the park and other regions along the coast since 2024. The NSF Center for Pandemic Insights at UC Davis and UC Santa Cruz have been working together to increase surveillance at this site over the past two months in anticipation of a possible outbreak in seals.

The scientific team is now working closely with NOAA Fisheries, the California Department of Fish and Wildlife and the West Coast Marine Mammal Stranding Network to continue to monitor marine mammals along the coast.

“We are cautiously optimistic, as most of the adult females had already departed the beach for their routine migrations before the outbreak began, and most seals on the colony seem healthy,” Beltran said.

​Continued: https://news.ucsc.edu/2026/02/first...thern-elephant-seals-confirmed-in-california/
 
Avian Influenza Confirmed in Northern Elephant Seals

February 26, 2026

Recently, scientists confirmed that a small number of young northern elephant seals at Año Nuevo State Park tested positive for highly pathogenic avian influenza (H5N1), also known as bird flu.

This is the first time H5N1 has been detected in California’s marine mammal population, and the first time it has been detected in northern elephant seals.

This development is especially concerning because the disease caused mass die-offs in a closely related species, southern elephant seals, during an outbreak in Argentina in 2023. That event showed how quickly this disease can spread through vulnerable marine mammal populations, underscoring the urgency of early detection, close monitoring and rapid response.

While most of the northern elephant seal colony appears healthy, experts are closely monitoring the situation in California to understand potential impacts and how it may affect marine mammals along our coast.

The Marine Mammal Center is working alongside leading partners including NOAA, UC Davis, UC Santa Cruz, California Department of Fish and Wildlife, and California Department of Public Health to monitor wildlife health and guide a coordinated, science-based response. As of February 26, 2026, we have not identified any confirmed cases in patients currently receiving care at our hospital.

What this means for people and pets

The risk of H5N1 to the public remains very low. The most important thing you can do is help protect yourself and marine mammals by:
  • Staying at least 150 yards away from seals and other marine mammals
  • Never touching live or dead wildlife
  • Keeping dogs leashed on or near beaches
  • Reporting sick or injured marine mammals to our hotline at 415-289-SEAL (7325)
​...

https://www.marinemammalcenter.org/news/avian-influenza-confirmed-in-northern-elephant-seals
 
Detections of Highly Pathogenic Avian Influenza in Mammals


Last Modified: March 04, 2026​
...

State County Date Collected Date Detected HPAI Strain Species​
CaliforniaSan Mateo2/20/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/20/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/21/20262/27/2026EA H5N1Northern elephant seal
CaliforniaLos Angeles1/13/20262/24/2026EA H5N1Catalina Island fox
CaliforniaLos Angeles1/14/20262/24/2026EA H5N1Catalina Island fox
CaliforniaLos Angeles12/8/20262/24/2026EA H5N1Catalina Island fox

...

https://www.aphis.usda.gov/livestoc...ian-influenza/hpai-detections/mammals?page=3​
 
Aphis made changes to their original report that was posted on March 4, 2026 (see post #95 above).

The reported number of seals confirmed infected has changed: it is now listed as 7 with a 'date detected' of February 24, compared to the previous March 4 posting that showed 26 with a 'date detected' of February 27.


Detections of Highly Pathogenic Avian Influenza in Mammals


Last Modified: March 04, 2026
...
State County Date Collected Date Detected HPAI Strain Species
CaliforniaLos Angeles12/8/20252/24/2026EA H5N1Catalina Island fox
CaliforniaLos Angeles1/13/20262/24/2026EA H5N1Catalina Island fox
CaliforniaLos Angeles1/14/20262/24/2026EA H5N1Catalina Island fox
CaliforniaSan Mateo2/20/20262/24/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/20/20262/24/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/20/20262/24/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/20/20262/24/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/20/20262/24/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/20/20262/24/2026EA H5N1Northern elephant seal
CaliforniaSan Mateo2/20/20262/24/2026EA H5N1Northern elephant seal
​...

https://www.aphis.usda.gov/livestoc...ian-influenza/hpai-detections/mammals?page=2​
 
H5N1 bird flu spreads to sea otters and sea lions along San Mateo coast, wildlife experts say

By Susanne Rust
Staff Writer
March 12, 2026 1:20 PM PT

Researchers say the H5N1 bird flu outbreak in California elephant seals has spread to other marine mammals, including a sea otter and sea lion.
...
Department of Fish and Wildlife and the Marine Mammal Center announced they had found the virus in seven dead elephant seal pups collected from the beach at Año Nuevo State Park. That number is now 16, but Johnson said likely more will be confirmed in the weeks to come.

“This count reflects only the animals that have gone through sampling and confirmatory testing in multiple labs,” she said. “We know there are more animals with signs of infection that we have sampled that are being tested across the different laboratory systems.”

She said no other otters have been found, but a “handful” of California sea lions are “in the queue.” This kind of spillover, she said, is not unusual.
...
Patrick Robinson, the Año Nuevo reserve director, and a marine biologist at UC Santa Cruz, said 47 elephant seals on the mainland have died since the outbreak began, and the wildlife team is finding two new symptomatic and two dead animals every day.
...

https://www.latimes.com/science/sto...ns-along-san-mateo-coast-wildlife-experts-say
 
Excerpt from previous post (#98)

The strain the animals have contains a mutation allowing it to more easily transmit between mammals. It is also a different variation than the ones found in dairy cows and commercial poultry. This one is Eurasian in origin, first seen in 2022. It has been detected in birds that fly along the Pacific Flyway, and is responsible for a mass mortality event in 2023 in northern fur seals on an island in eastern Russia, said Christine Johnson, director of UC Davis’ Center for Pandemic Insights, during a press conference Thur​sday morning.

Johnson said researchers think this is the first detection of the A3 variation of the virus on the Pacific Coast and therefore likely a new introduction into North America, she said.
 
Deadly virus outbreak at Bay Area state park spreads to nearby beaches
March 12, 2026

Excerpt's

Though the outbreak is currently limited to San Mateo County, Johnson said experts have detected additional cases along the coastline just north and south of Año Nuevo State Park.

“We are starting to see some carcasses on public beaches,” she said. People are asked to contact the National Oceanic and Atmospheric Administration’s stranding hotline at 866-767-6114 to report any sightings. If you think you have been exposed to a sick animal on the beach and experience symptoms like a cough, runny nose, fever or shortness of breath, call your doctor and seek medical attention.​

https://www.sfgate.com/local/article/bay-area-virus-spreads-22073761.php
 
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