On October 14, the California Department of Fish and Wildlife, the San Diego Zoo Wildlife Alliance and the Ojai Raptor Center released the necropsy results for Patient 26-519, the bald eagle from Big Bear Valley known to millions as Jackie.

Veterinary pathologists confirmed Highly Pathogenic Avian Influenza (HPAI) as the primary underlying cause of her decline, following extensive laboratory and toxicology testing by the California Animal Health and Food and Safety Laboratory at UC Davis, with final HPAI confirmation by the USDA National Veterinary Services Laboratory system.

The presentation was highly unusual: instead of the neurological signs typical of HPAI in raptors, the infection caused a severe ulcer in Jackie's gizzard that led to persistent internal bleeding, severe anemia, and bacterial sepsis, along with inflammation and blood clots in her heart and major vessels.

According to Yahoo, Dr. William Bowerman, a University of Maryland wildlife ecology professor who has studied bald eagles since the 1980s, said 'Nobody knew this was even a probability' — there was no active bird flu outbreak in Southern California this year, and he noted the virus wasn't believed to be widely circulating when she fell ill.

Jackie was rescued on July 17 after an altercation with two subadult eagles near Dana Point Park, found grounded and unable to fly, and transferred to the Ojai Raptor Center, where she was diagnosed with severe anemia.

Popular Science reports her condition worsened in early August, and she died the morning of August 10.

Her caretakers had explored many potential causes — lead poisoning, zinc toxicity, rodenticide, cancer — and at one point gave her a blood transfusion, because bird flu was never the suspected culprit.

The testing narrowed a crowded field of suspects. CDFW reported Jackie tested negative for West Nile Virus, and heavy metals including lead were within acceptable limits, not tied to her disease progression.

Toxicology did detect brodifacoum, an anticoagulant rodenticide, in her liver, along with persistent environmental contaminants — but the necropsy found no uncontrolled bleeding of the kind rodenticide causes, so it was not identified as the primary cause of her death.

Jackie's death removes one half of the iconic bald eagle pair whose nest camera livestream made them worldwide favorites. CDFW confirmed her mate Shadow remains in Big Bear Valley, and that camera data show no evidence Shadow or this year's eaglets were sick.

According to ABC News, a new female eagle known as KD1 — called 'Katie' by fans — has recently been spending time with Shadow. Consistent with HPAI protocols, Jackie's remains were cremated by the U.S. Fish and Wildlife Service's National Eagle Repository.

Because HPAI wasn't initially suspected, Jackie received extensive testing and treatment that birds with a typical presentation never would — Yahoo reports Bowerman said her case 'gave us more science than we were expecting,' though a necropsy cannot determine how or when she was infected; she may have eaten infected waterfowl or carried the virus dormant for years.

CDFW Director Meghan Hertel said understanding the results can inform care of other eagles, and Popular Science notes supporters can donate to Friends of Big Bear Valley or Ojai Raptor Center's Bald Eagle Recovery Campaign in her memory.