Avian Flu in California Seals: First Cases Confirmed at Año Nuevo
California health officials are investigating the first confirmed cases of highly pathogenic avian influenza (HPAI) H5N1 in northern elephant seals, detected at Año Nuevo State Park. The outbreak, confirmed on , marks the first instance of the virus in marine mammals within the state and the first detection specifically in northern elephant seals.
The affected animals are seven weaned elephant seal pups. Researchers at UC Santa Cruz and UC Davis had increased disease surveillance in recent years, anticipating the potential for avian influenza to spread to this vulnerable population. “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.
This detection is particularly significant given the rapid pace at which the outbreak was identified. “This is exceptionally rapid detection of an outbreak in free-ranging marine mammals,” noted Professor Christine Johnson, director of the Institute for Pandemic Insights at the UC 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.”
The current H5N1 outbreak has a concerning history. Originally discovered in in Southeast China on a domestic goose farm, the virus initially spread within the poultry industry before spilling over into wild birds and humans. It subsequently reached Europe, the Middle East, Africa and both North and South America, and even Antarctica by early .
The North American outbreak began in early winter in Newfoundland and Labrador, Canada, and has since been confirmed in nearly all U.S. States and Canadian provinces. It has impacted commercial poultry, backyard flocks, numerous wild bird species, and several mammal species, including humans. Prior to this latest development, HPAI outbreaks were documented in U.S. Marine mammals in Maine in and Washington in , both resulting from direct transmission from infected birds to seals.
Researchers at UC Davis have been actively testing samples from marine birds and mammals since , and the NSF Center for Pandemic Insights at UC Davis and UC Santa Cruz have intensified surveillance at Año Nuevo State Park over the past two months. The scientific team is collaborating with NOAA Fisheries, the California Department of Fish and Wildlife, and the West Coast Marine Mammal Stranding Network to monitor marine mammals along the coast.
While the situation is being closely monitored, officials express cautious optimism. Beltran noted that most adult female seals had already begun their routine migrations prior to the outbreak, and the majority of seals remaining at the colony appear healthy. However, the potential for further spread and impact on the population remains a concern.
Public health officials emphasize that the risk of infection to the general public is low, but HPAI can spread between animals and people. The public is strongly advised to maintain distance from both live and deceased seals and to prevent pets from approaching them. This precaution is intended to protect both human and animal health and to minimize stress on potentially sick animals.
Anyone who encounters a sick, injured, or deceased marine mammal in California, Oregon, or Washington is urged to contact the NOAA Fisheries West Coast Region Stranding Hotline at . This proves crucial not to attempt to move sick wild animals, as this could exacerbate the spread of disease and cause further harm.
Ongoing wildlife surveillance and monitoring are considered critical for preventing and detecting future outbreaks globally. The NSF Center for Pandemic Insights at UC Davis is actively developing innovative technologies – including chemical sensors and drones – to enhance HPAI surveillance, particularly in populations that are less frequently monitored.
The team will provide weekly updates and continue to monitor the situation closely, conducting drone surveys and analyzing samples from affected animals. Further information about the outbreak is available on the Institute for Pandemic Insights website.