07 May 2026
In a historic medical finding, researchers confirmed the first human case of fatal highly pathogenic avian influenza A(H5N5) worldwide. The Washington resident, a backyard flock owner, died following a complex diagnostic course involving multiple false-negative tests.
The patient, an individual aged 65 with a history of non-Hodgkin lymphoma, developed symptoms in late October 2025 including fever, cough, and diarrhea. For the first 14 days of illness, multiple upper respiratory (nares) swabs tested negative for influenza A. It was only on day 15, after the patient was transferred to an intensive care unit and underwent a bronchoalveolar lavage, a procedure where fluid is squirted into the lungs and then collected, that the A(H5) virus was detected. Investigation of the patient's property revealed that while their backyard ducks appeared healthy, they were shedding the virus. Genomic sequencing confirmed that the virus found in the patient was highly genetically similar to samples taken from the ducks and the sediment of their watering basin. Despite aggressive treatment with four different antiviral medications, the patient succumbed to acute respiratory failure 28 days after symptom onset.
Kibiger, L., Oltean, H. N., Leitz, L., et al. (2026). Fatal Human Case of Highly Pathogenic Avian Influenza $A(H5N5)$ in a Backyard Flock Owner - Washington, November 2025. Morbidity and Mortality Weekly Report (MMWR), 75(17), 221–225.
See: First Death From H5N5 Avian Influenza
