Deadly Avian Flu Detected in Marin County After Spreading to Marine Mammals in California

A deadly strain of avian flu has been detected in Marin County’s Kehoe Beach, marking the second Bay Area location where the virus has infected seabirds and marine mammals. The discovery follows a recent outbreak in San Mateo County’s Año Nuevo State Park, where the virus—known to be highly pathogenic—was detected in marine mammals for the first time in California. Health officials from the California Department of Public Health (CDPH) and the National Park Service (NPS) confirmed the presence of the virus in a dead common murre collected from Kehoe Beach on March 10, as part of a broader regional mortality event affecting seabirds across the Bay Area.

Deadly Avian Flu Spreads to Second Bay Area Location, Raising Regional Concerns

Biologists with the National Park Service (NPS) first noticed an unusual number of dead common murres at Kehoe Beach in Point Reyes National Seashore on February 25. Preliminary tests conducted by the U.S. Geological Survey’s National Wildlife Health Center confirmed the presence of avian flu in one of three deceased birds recovered from the site. The findings come just weeks after the virus was detected in marine mammals at Año Nuevo State Park, a 30-mile stretch of coastline in San Mateo County, where northern elephant seals and other species tested positive for the highly pathogenic H5N1 strain.

How the Outbreak Unfolded: From Seabirds to Marine Mammals

The timeline of the outbreak traces back to late January, when wildlife biologists began documenting an uptick in dead seabirds along the California coast. By February, the virus had jumped to marine mammals, a previously unseen phenomenon in the state. At Año Nuevo State Park, 27 northern elephant seals tested positive for H5N1, with at least 47 fatalities recorded. The spread to Kehoe Beach—nearly 100 miles north of Año Nuevo—expands the geographic footprint of the outbreak, raising concerns about its potential to destabilize marine ecosystems.

Earl Perez-Foust, a spokesperson for the NPS, noted that while the increase in dead birds at Kehoe Beach aligns with a broader regional seabird mortality event, no signs of illness have been confirmed in the northern elephant seal colony at Point Reyes National Seashore. ‘We’re monitoring the situation closely,’ Perez-Foust said. ‘While the virus has not been detected in local elephant seals, we’re taking every precaution to prevent further spread.’

Avian Flu’s Unprecedented Jump to Marine Mammals Puzzles Scientists

The detection of H5N1 in marine mammals represents a significant and concerning development in the outbreak. Historically, avian flu has primarily affected poultry and wild birds, but the recent cases in California mark the first time the virus has been confirmed in marine mammals in the state. Experts are still investigating how the virus made the leap from birds to seals and sea lions, though theories include direct contact with infected seabirds or exposure through contaminated water.

‘This is a dynamic and evolving situation,’ said Dr. Erica Pan, California’s state public health officer. ‘While the risk to the general public remains very low, we’re seeing an unprecedented event where a bird flu strain is infecting marine mammals. This underscores the need for vigilance and caution.’

The outbreak has also affected other marine species, including California sea lions, fur seals, and sea otters. A recent press conference held by UC Davis’ Institute for Pandemic Insights revealed that at least two sea lions and one southern sea otter have tested positive for the virus, with an additional sea lion infection confirmed this week. Additionally, western gulls and Brandt’s cormorants have been impacted, while a population of peregrine falcons has been declining for years due to the same strain of the virus, according to a study from UC Santa Cruz.

Health Officials Urge Caution as Human Risk Remains Low

Despite the alarming spread of the virus among wildlife, health officials emphasize that the risk to humans is currently low. The CDPH and the Centers for Disease Control and Prevention (CDC) have stated that there is no evidence of human-to-human transmission of H5N1 in this outbreak. However, they caution that infection can occur if the virus enters the eyes, nose, or mouth, or is inhaled during close unprotected contact with infected animals or contaminated surfaces.

How to Protect Yourself and Your Pets

Public health experts are urging beachgoers to take precautions to avoid exposure. The NPS and the Marine Mammal Center have issued guidance for the public to maintain a safe distance from sick or dead wildlife and to keep pets leashed and away from animals. Reporting sightings of unhealthy animals to park staff is critical for monitoring the outbreak.

• Avoid approaching or handling sick or dead wildlife, including seabirds and marine mammals.
• Keep pets leashed and away from animals that appear unwell.
• Report sightings of unhealthy wildlife to park staff or local authorities immediately.
• Wear personal protective equipment (gloves, eye protection, masks) when handling wildlife.
• Monitor for influenza-like symptoms if exposed to sick animals and seek medical attention if necessary.

Wildlife Rescues Pause Operations Out of Caution

In response to the outbreak, the Marine Mammal Center has temporarily paused its efforts to respond to northern elephant seals and harbor seals due to safety concerns. ‘Keeping our volunteers and staff safe from a human health perspective is our number one priority,’ said Giancarlo Rulli, a spokesperson for the center. However, the center continues to respond to other species, including California sea lions, fur seals, and sea otters. Beachgoers can report sick or dead animals to the center’s hotline at 415-289-SEAL.

Long-Term Concerns: Ecosystem Impact and Future Monitoring

The long-term implications of this outbreak are still unclear, but scientists are concerned about the potential impact on marine ecosystems. The decline in seabird populations, such as common murres and Brandt’s cormorants, could disrupt food chains and affect other species that rely on them for survival. Additionally, the infection of marine mammals raises questions about the virus’s ability to adapt to new hosts, which could have broader implications for wildlife conservation efforts.

Ongoing Research and Data Collection

Researchers at UC Davis and other institutions are continuing to monitor the situation and collect data on affected species. For example, scientists at the Marine Mammal Center are tracking the health of individually flipper-tagged northern elephant seals and documenting their symptoms. This data will be critical for understanding the virus’s behavior and developing strategies to mitigate its impact.

What This Means for California’s Wildlife and Public Health

The detection of H5N1 in multiple species across the Bay Area underscores the need for a coordinated response from wildlife agencies, public health officials, and conservation groups. While the immediate risk to humans is low, the outbreak serves as a reminder of the interconnectedness of ecosystems and the potential for zoonotic diseases to emerge in unexpected ways. As scientists work to unravel the complexities of this event, public awareness and caution remain essential.