Avian Flu Spreads Further Along California Coast, Raising Concerns for Marine Wildlife
A highly pathogenic avian influenza (HPAI) H5N1, initially detected in northern California last month, is now confirmed in San Luis Obispo County, marking the first case in a marine mammal from that region. The virus, which has already impacted elephant seals and sea lions, continues to spread, prompting increased monitoring and concern from wildlife experts.
First Case in San Luis Obispo County Confirmed
On March 25th, UC Davis and the USDA’s National Veterinary Services Laboratory confirmed the presence of H5N1 in a deceased California sea lion found on Morro Strand State Beach in Morro Bay. The animal, estimated to be one to two years old, is the third sea lion to test positive for the virus, with the previous two cases identified in San Mateo County. Researchers from the Central California Marine Animal Response Team (CCMART) collected the sample on March 16th.
Expanding Geographic Range and Species Affected
The spread of the virus is particularly concerning due to the mobility of juvenile sea lions. They forage along the central California coast, traveling as far south as the Channel Islands, potentially expanding the outbreak’s reach. Beyond sea lions, the virus has been detected in 27 northern elephant seals, resulting in at least 47 deaths. A southern sea otter has also tested positive for the disease.
Avian Impact and Broader Regional Concerns
The outbreak isn’t limited to marine mammals. A dead common murre at Point Reyes National Seashore tested positive earlier this month, coinciding with an increase in deceased seabirds across the Bay Area. This points to a broader regional seabird mortality event. Although no illness has been confirmed in the northern elephant seal colony at Point Reyes, officials are maintaining vigilance.
Public Health Guidance and Reporting
While the risk of transmission to humans remains low, the public is advised to maintain a safe distance from marine mammals and seabirds, especially those appearing sick or deceased. Individuals should not approach, touch, or attempt to assist these animals.
Sightings of sick or injured marine mammals should be reported to the NOAA West Coast Marine Mammal Stranding Hotline at 866-767-6114. Sick or injured birds can be reported to the California Department of Fish and Wildlife at 916-358-2790.
Understanding the Virus and its Adaptation
Studies from UC Davis have shown that H5N1 is increasingly adapting to mammals, a development with potentially global consequences. Genomic analysis reveals the virus is evolving into separate avian and marine mammal clades in South America, a previously unseen phenomenon. This adaptation increases the potential for transmission between species, including humans.
Frequently Asked Questions
What is H5N1? H5N1 is a strain of avian influenza, commonly known as bird flu, that can infect birds and, less frequently, mammals.
Is H5N1 dangerous to humans? While the risk is currently low, H5N1 has the potential to infect humans and cause severe illness. Ongoing monitoring is crucial.
What should I do if I find a sick or dead marine mammal? Do not approach the animal. Contact the NOAA West Coast Marine Mammal Stranding Hotline at 866-767-6114.
Is it safe to visit beaches in affected areas? Yes, but maintain a distance of at least 150 yards from all marine mammals and seabirds.
What is being done to monitor the outbreak? Researchers are actively monitoring marine mammal and seabird populations along the California coast, conducting genomic analysis to track the virus’s evolution.
Did you recognize? The outbreak among elephant seals in Argentina in 2023 marked the first known transnational spread of H5N1 in mammals globally.
Pro Tip: Stay informed about the latest updates on avian influenza by visiting the UC Davis Pandemic Insights website: https://pandemicinsights.ucdavis.edu/h5-marine-outbreak
Stay updated on this evolving situation and help protect California’s marine wildlife by reporting any concerns to the appropriate authorities. Share this information with your friends and family to raise awareness.
