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California - Avian flu in mammals and livestock 2025-2026

Año Nuevo State Park​
The Park is currently OPEN WITH RESTRICTIONS IN SERVICES AND/OR FACILITIES.

Please check the hours of operation.​

Current Restrictions
Last Checked: 3/13/2026 3:52 AM

Año Nuevo State Park has temporarily closed public access to the elephant seal viewing area and Año Nuevo Coast Natural Preserve while park staff and wildlife health partners evaluate a small number of recent seal illnesses. At this time, tours have been canceled through March 1st with full refunds available through Reserve California (ReserveCalifornia or 1-800-444-4445). Most seals on the beach appear healthy. Out of an abundance of caution, access is being paused to give wildlife space and allow for ongoing monitoring. We appreciate your patience and understanding as this is a popular time to visit the park to view these beloved animals in their natural habitat. Updates will be provided through social media channels (facebook instagram) and website as more information becomes available. Those interested in viewing the elephant seals can do so via the Año Nuevo Mainland Camera.​

https://www.parks.ca.gov/?page_id=523
 
I found the following explanation yesterday afternoon on a recently updated Genoflu upadate by NVSL at the following site:

https://github.com/USDA-VS/GenoFLU?tab=readme-ov-file

The current “D” genotypes represent reassortants of GenoFlu A3 that emerged in the late fall/winter of 2024 (Figure 1 and Table 1). Genotype D1.1, a four gene reassortant of A3 with North American genes, including N1, replaced previous B3 genotypes by late 2024 and is currently the most frequently detected genotype since the start of this event. Circulation of genotype A3 remained limited to the Pacific flyway until late fall and winter of 2024, when A3 and the “D” genotypes expanded eastward, affecting wild birds, poultry, and wild mammals across all four migratory flyways. The D1.1 genotype has affected poultry, spilled over into mammals, and affected a small number of dairy cattle herds in three different states (AZ, NV, WI), and continues to evolve with new genotypes (D1.5, D1.6 [AM N2], D1.11 [AM N5]) identified to date.

So A3 has been around since 2024; however, it is a progenitor to the now more prominent D-series.
 
Institute for Pandemic Insights

​H5 Influenza A Outbreak in Marine Mammals

Situation Update
(screenshot)
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03/12/2026: A recording of the Press Briefing held today can be viewed here.

03/10/2026: Scientists have confirmed a case of HPAI H5N1 in a California sea lion in San Mateo County, California. The adult male sea lion was found dead on February 27 near Año Nuevo State Reserve by the California Academy of Sciences. Samples were sent to UC Davis and the USDA’s NVSL laboratory, where presence of the virus was confirmed on March 9. To date, all positive HPAI H5N1 cases have been detected in San Mateo County. A network of responders continue to investigate stranded or dead marine mammals in neighboring areas to assess influenza activity in seals, sea lions, and sea otters. People and their pets should avoid all contact with sick or dead wildlife and can report dead or distressed marine mammals on the west coast to the NOAA Fisheries West Coast Region Stranding Hotline: (866) 767-6114.

03/06/2026: Scientists have confirmed a case of HPAI H5N1 in a southern sea otter in San Mateo County, California. The southern sea otter was found dead by UC Santa Cruz researchers on February 26. A postmortem examination was conducted by trained wildlife disease experts at the California Department of Fish and Wildlife’s Marine Wildlife Veterinary Care & Research Center in Santa Cruz, and samples were sent to UC Davis and the USDA’s NVSL lab, where presence of the virus was confirmed on March 5. Researchers continue to monitor marine mammal populations to understand the full extent and impact of the disease outbreak.

03/05/2026: We are continuing to monitor progression of the outbreak and investigate the impact to animals. To date, approximately 60 marine mammals are currently being tested for suspected influenza virus infection at Año Nuevo State Park. In addition, we are evaluating stranded or dead marine mammals in neighboring areas to determine if influenza has spread to other species or other regions. If new cases are confirmed, updates will be posted to this site.

02/25/2026: On February 19th and 20th, multiple northern elephant seal weanling pups (recently weaned from nursing) were observed dead at Año Nuevo State Park in San Mateo County, California. Live elephant seal weanlings were also observed with tremors and seizure activity. In collaboration with University of California, Davis, researchers from University of California, Santa Cruz responded to collect samples from 7 sick and dead animals for testing at the California Animal Health & Food Safety Laboratory System (CAHFS) laboratory at UC Davis. Initial screening revealed that the samples were positive for influenza A, subtype H5. The USDA National Veterinary Services Laboratory (NVSL) later confirmed infection with influenza A subtype H5N1 (Highly Pathogenic Avian Influenza, HPAI).

https://pandemicinsights.ucdavis.edu/h5-marine-outbreak​
 
Essay from a must read account -

hat tip Hogvet51

snip

"A post by Pathfinder last night in Flutrackers covered an article in the LA Times written by Susanne Rust regarding the outbreak in sea mammals:

H5N1 bird flu spreads to sea otters and sea lions along San Mateo coast, wildlife experts say.

A quote from the article was added in a nested FluTrackers post from Commonground:

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.
​
snip

In reviewing the GitHub genotype reference table, it appears that A3 produces long lists of “children” isolates - over 60 “minor” genotypes, some of which may become successful enough to gain “D-lettered” status. We’ll see if A3 itself or a D-descendent becomes a “King Kong” in marine mammals…like D1.1 has done in domestic poultry and wildlife currently.​"

more...https://hogvet51.substack.com/p/h5n1-in-us-marine-mammals-website?utm_source=post-email-title&publication_id=2578829&post_id=190850431&utm _campaign=email-post-title&isFreemail=true&r=4qjp7k&triedRedirect=true& _src_ref=webmail1.earthlink.net&utm_medium=email
 
Institute for Pandemic Insights

​H5 Influenza A Outbreak - Press
Briefing Video UC Davis

Press Briefing - H5N1 Outbreak
March 12, 2026

Panelists include:
  • Christine Johnson, Director, Institute for Pandemic Insights, UC Davis
  • Patrick Robinson, Patrick Robinson, Año Nuevo Reserve Director, UC Santa Cruz
  • Moe Flannery, Sr. Collection Manager, California Academy of Sciences
  • Dominic Travis, Chief Programs Officer, The Marine Mammal Center
  • Catherine Sallenave, Infectious Diseases Staff Physician, San Mateo County
​https://pandemicinsights.ucdavis.edu/h5-influenza-outbreak-press
 
Avian Flu Not Found in Area Elephant Seals

Written by Theresa-Marie Wilson
...
March 13, 2026
...
Currently, about 35 marine mammals are being tested for suspected influenza virus infection at Año Nuevo, but what about our rookery at Piedras Blancas in San Simeon? As of March 5, the elephant seals who breed in the area have not been affected, which is good news, but caution is still in play.

“As far as we have seen, it looks like the virus spilled over from birds to seals, but there is no evidence of seal-to-seal transmission at this point. That means it is unlikely that seals will bring the virus down from Año Nuevo” Heather E.M. Liwanag, Ph.D., a Cal Poly professor who runs the team that is monitoring the local population. told Estero Bay News. “It is possible that we could get spillover from birds to seals here, like what happened at Año Nuevo. We have been worried about that for a few years now, and the event at Año Nuevo is the first time we have seen it happen.”
...
Signs of the bird flu include “abnormal respiratory and neurological signs, including weakness and tremors,” Halaska said. “All the animals that were seen with these symptoms were found dead 24 hours later. At this point only weaned elephant seal pups are those being affected at a small, contained section of Año Nuevo Reserve.

“This age-class, weaned pups, are learning how to swim, forage on their own and adjusting to life without mom present. They are not able to swim very long or far and spend most of their time on shore near where they were birthed. Additionally, the animals that are displaying the HPAI symptoms are dying withing 24hrs.”
...

https://esterobaynews.com/featured-stories/avian-flu-not-found-in-area-elephant-seals/
 
Commonground said:
Institute for Pandemic Insights

​H5 Influenza A Outbreak - Press
Briefing Video UC Davis

Press Briefing - H5N1 Outbreak
March 12, 2026

Panelists include:
  • Christine Johnson, Director, Institute for Pandemic Insights, UC Davis
  • Patrick Robinson, Patrick Robinson, Año Nuevo Reserve Director, UC Santa Cruz
  • Moe Flannery, Sr. Collection Manager, California Academy of Sciences
  • Dominic Travis, Chief Programs Officer, The Marine Mammal Center
  • Catherine Sallenave, Infectious Diseases Staff Physician, San Mateo County
​https://pandemicinsights.ucdavis.edu/h5-influenza-outbreak-press
Click to expand...

I was told by a major, experienced, global, avian flu reporter that no UC Davis official would respond to inquiries when the H5N1 outbreak occurred in dairy cows. Things must have really progressed.
 
From Post #100:

March 13, 2026, 06:00 AM
Año Nuevo State Park​
The Park is currently OPEN WITH RESTRICTIONS IN SERVICES AND/OR FACILITIES.
Please check the hours of operation.​
Current Restrictions
Last Checked: 3/13/2026 3:52 AM

Año Nuevo State Park has temporarily closed public access to the elephant seal viewing area and Año Nuevo Coast Natural Preserve while park staff and wildlife health partners evaluate a small number of recent seal illnesses. At this time, tours have been canceled through March 1st with full refunds available through Reserve California (ReserveCalifornia or 1-800-444-4445).​..
Click to expand...


GUIDED ELEPHANT SEAL TOURS CANCELLED FOR REMAINDER OF SEASON.

Año Nuevo State Park has closed public access to the elephant seal viewing areas for the remainder of the season after receiving confirmation that seven weaned elephant seal pups have tested positive for the highly pathogenic avian influenza (HPAI) H5N1.

Tours have been cancelled with full refunds being issued through Reserve California. The park will continue working with partners and will rely on experts to determine when it is safe to reopen closed areas.

Our Marine Education Center, Horse Barn Movie Theater and 3/4mi of the Año Nuevo Point Trail will remain open at this time.

https://www.parks.ca.gov/?page_id=523
​
 
Source: https://www.slocounty.ca.gov/depart...po-county-tests-positive-for-h5n1-(bird-flu)/

Deceased Sea Lion Found in San Luis Obispo County Tests Positive for H5N1 (Bird Flu)

Author: Public Health
Date: 3/27/2026 2:07 PM


While the risk of H5N1 to the public remains low, officials ask community members and visitors to avoid approaching marine mammals and seabirds and report them instead through the appropriate channels.

San Luis Obispo, Calif— A deceased sea lion found along Morro Strand State Beach has tested positive for H5N1 (avian influenza or bird flu), marking the first confirmed case in a marine mammal in the county.

While the risk of H5N1 to the public remains low, officials from San Luis Obispo County Public Health Department, the California Department of Fish & Wildlife, and the Central California Marine Animal Response Team urge community members and visitors to avoid approaching marine mammals and seabirds. This is especially important for animals that appear sick, injured, or deceased.​..
 
California: SLO County Reports Dead Sea Lion From H5N1


AVvXsEgge7y6-2bJSn_ySYAm9rjaAoi4NKtEbvyk15ZdP7lHBuJWcq3mpzVBjF9k-Fa2BrdDqdUYHj39dTygu5PEWBnJ5WDhHOMcOZwLDFxybCgLvbiNpP6Js4BGHpkD-xPhFbkRbFlX0mW_GUv_HZkROrCZGZM3ScxuajCv1SBKYTL5BnL0OzyPvSjkeQ=w320-h300

California Marine Mammals with H5N1

#19,099

Just over a month ago the Año Nuevo Natural Reserve in San Mateo County, CA announced the first U.S. detection of H5N1 in Elephant Seals after dozens of seals were observed either sick or dying and the virus was confirmed by the USDA’s NVSL lab.

Since then, according to local news outlets (see CIDRAP report), the number of HPAI positive seals has increased, along with an H5 positive otter and a sea lion. The actual count is likely much higher, as only a limited number of mammals have been tested.​

In early March we saw an update and health advice from California's DPH and just over a week ago a paper on the impact of HPAI H5 on pinnipeds (see UC Davis: High pathogenicity Avian Influenza in Pinniped conservation).

Late yesterday, SLO (San Luis Obispo) county announced the discovery of a dead sea lion (H5N1 positive) on Morro Strand State Beach - some 150 miles south of the first outbreak - in the following press release.

Deceased Sea Lion Found in San Luis Obispo County Tests Positive for H5N1 (Bird Flu)

Author: Public Health
Date: 3/27/2026 2:07 PM

While the risk of H5N1 to the public remains low, officials ask community members and visitors to avoid approaching marine mammals and seabirds and report them instead through the appropriate channels. En español

San Luis Obispo, Calif— A deceased sea lion found along Morro Strand State Beach has tested positive for H5N1 (avian influenza or bird flu), marking the first confirmed case in a marine mammal in the county.

While the risk of H5N1 to the public remains low, officials from San Luis Obispo County Public Health Department, the California Department of Fish & Wildlife, and the Central California Marine Animal Response Team urge community members and visitors to avoid approaching marine mammals and seabirds. This is especially important for animals that appear sick, injured, or deceased.

“Staying 150 yards away from all marine mammals and seabirds; keeping children and pets away from sick, injured or dead wildlife; and not approaching, touching or attempting to assist marine mammals or seabirds,” states guidance from the California Department of Public Health.

Officials ask the public not to touch or help wildlife and instead to call:​

“While the risk to the public remains low, it’s understandable that people may have questions about their own health if they find themselves unexpectedly exposed to a sick or dead animal,” said County Health Officer, Dr. Penny Borenstein. “If community members have questions about H5N1 as it relates to human health, our Public Health Department can help answer those questions.”

Community members can reach the County of SLO Public Health Department by calling 805-781-5500. To learn more about H5N1 in California by visiting the California Department of Public Health’s bird flu webpage or by reading updates from UC Davis regarding recent H5N1 activity in marine mammals.

History of bird flu in SLO County​
Positive cases of bird flu have been found in SLO County since 2022 from various wild birds within the county. In 2024, many states, including California, experienced outbreaks of H5N1 in dairy cattle. There were 38 confirmed human cases in California linked to exposures from infected cattle between September 2024 and January 2025 with none in SLO County.​


UC Davis maintains an H5 Influenza A Outbreak in Marine Mammals webpage which now lists 28 Elephant Seals, 2 Sea Lions, and 1 otter as having tested positive in California over the past 6 weeks.




Compared to what we've seen in South America, this remains a small outbreak, but it is likely we are only seeing the tip of the iceberg. Many animals may have died unnoticed at sea, or have washed up on remote beaches.

Although H5N1 has yet to crack the `transmission code' in humans, evidence suggests marine mammals may be closer to achieving sustained transmission (see Preprint: Massive outbreak of Influenza A H5N1 in elephant seals at Peninsula Valdes, Argentina: increased evidence for mammal-to-mammal transmission).​

While that would be a terrible thing for marine mammals, it might not work out too well for us, either.


https://afludiary.blogspot.com/2026/03/california-slo-county-reports-dead-sea.html
​
 
Related to Shiloh's and Michael Coston's posts above:

H5 Influenza A Outbreak in Marine Mammals

Situation Update
  • 03/26/2026: Scientists have confirmed a case of HPAI H5N1 in a California sea lion in San Luis Obispo County, California. The young (1-2 year old) dead sea lion was sampled by a researcher from Central California Marine Animal Response Team (CCMART) on March 16, and samples were sent to UC Davis and the USDA’s NVSL lab where presence of the virus was confirmed on March 25. This is the first report of HPAI in a marine mammal from San Luis Obispo County which is south of the main outbreak response area in San Mateo County. Juvenile sea lions are known to forage along the central California coast traveling as far south as the primary sea lion breeding colonies on the Channel Islands. Researchers are continuing to monitor marine mammal populations all along the coast.
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​https://pandemicinsights.ucdavis.edu/h5-marine-outbreak
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Bay Area coastal preserve to reopen after bird flu kills dozens of elephant seals

​Posted: Apr 8, 2026 / 07:52 AM PDT
Updated: Apr 8, 2026 / 07:52 AM PDT


PESCADERO, Calif. (KRON) — The natural preserve at Año Nuevo State Park on the San Mateo County coast, where thousands of elephant seals gather each winter to breed, is set to reopen to the public for the first time since an outbreak of avian influenza killed at least 95 to 100 of the mammoth marine mammals.

“Thanks to the tireless efforts of our researchers and scientists, as well as all the staff who support them, we are pleased to announce that the Marine Preserve and elephant seal viewing areas will be open starting April 11,” park officials announced Tuesday.
​
-snip-
By March 20, Año Nuevo Reserve Director Patrick Robinson said the estimated total number elephant seal deaths from HPAI on the mainland beaches reached about 50, plus another 45 to 50 on Año Nuevo Island, situated a half mile offshore. At that time, UC Santa Cruz researchers were finding an average of two newly dead and two newly symptomatic animals every day.​
​
...https://www.kron4.com/news/bay-area...fter-bird-flu-kills-dozens-of-elephant-seals/
 
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