We are writing to share that several cases of highly pathogenic avian influenza (HPAI) have been confirmed in northern elephant seals at Año Nuevo State Park in San Mateo County, California. For more information: A press release is available here <https://www.ucdavis.edu/health/news/first-cases-highly-pathogenic-avian-influenza-northern-elephant-seals-confirmed-california>. Situation updates are available at the UC Davis Institute for Pandemic Insights here <https://pandemicinsights.ucdavis.edu/h5-marine-outbreak>. Scientists at UC Santa Cruz and UC Davis are working closely with the National Oceanic and Atmospheric Administration (NOAA Fisheries), California State Parks, California Department of Fish and Wildlife (CDFW), California Department of Public Health (CDPH), local health officials, The Marine Mammal Center (TMMC), the West Coast Marine Mammal Stranding Network, and other agencies and research partners.