tetano
Editor, Senior Moderator
MMWR Morb Mortal Wkly Rep
. 2026 May 7;75(17):221-225.
doi: 10.15585/mmwr.mm7517a2.
Fatal Human Case of Highly Pathogenic Avian Influenza A(H5N5) in a Backyard Flock Owner - Washington, November 2025
Lynae Kibiger, Hanna N Oltean, Lisa Leitz, Emma Krause, Debra Barrett, Anna Halloran, Kyle Yomogida, Beth Lipton, Keely Paris, Jared Keirn, Minden Buswell, Allison Black, Pauline Trinh, Theresa Murray, Roberto Bonaccorso, Leticia Banuelos, Ethan Dieringer, Jennifer Lenahan, Emily Spence Davizon, Ellyn P Marder, Jocelyn Mullins, Meagan Kay, Eric J Chow, Sandra J Valenciano, John Lynch, Vanessa Makarewicz, Chloe Bryson-Cahn, Jennifer Hernandez, Kyla Haggith, Valicia Linn, Alex L Greninger, Stephanie Goya, Sierra Gulla, Jennifer Young, Sierra Kerns-Funk, Brianna da Silva Bhatia, Hollianne Bruce, Krista Kniss, Katie Reinhart, Rachel Ohlstein, Shannon Johnson, Christina Schofield, Patrick Smith, Amber Itle, Maura Gibson, Brandi Torrevillas, Azeza Falghoush, Thomas B Waltzek, Kevin Snekvik, Mia Torchetti, Timothy M Uyeki, Scott Lindquist
Clade 2.3.4.4b influenza A(H5N1) viruses have circulated across migratory bird flyways in the United States since 2022, including in Washington, where backyard flock detections have been reported annually. In November 2025, a Washington resident died from acute respiratory failure after receiving a positive influenza A(H5) test result at a hospital laboratory. Washington Public Health Laboratories confirmed influenza A(H5), and genomic sequencing identified influenza A(H5N5) virus (A6 genotype). Polymerase chain reaction testing detected highly pathogenic avian influenza A(H5) virus clade 2.3.4.4b from an apparently healthy backyard flock of ducks and sediment from a watering basin on the patient's property. Six of eight gene segments from the environmental sample and one duck sample (partial neuraminidase segment) were highly genetically similar to the patient's virus sequence. Although existing wild bird surveillance had not detected influenza A(H5N5) virus (A6) in the U.S. Pacific Flyway, introduction via wild birds into the environment of the backyard flock was likely the source of the patient's exposure. The public health investigation identified approximately 135 exposed persons; symptom monitoring and influenza testing detected no additional cases. The overall risk for avian influenza A remains low among the general U.S. population; however, novel avian influenza A virus infection should be considered in persons with symptoms of influenza and potential exposures.
. 2026 May 7;75(17):221-225.
doi: 10.15585/mmwr.mm7517a2.
Fatal Human Case of Highly Pathogenic Avian Influenza A(H5N5) in a Backyard Flock Owner - Washington, November 2025
Lynae Kibiger, Hanna N Oltean, Lisa Leitz, Emma Krause, Debra Barrett, Anna Halloran, Kyle Yomogida, Beth Lipton, Keely Paris, Jared Keirn, Minden Buswell, Allison Black, Pauline Trinh, Theresa Murray, Roberto Bonaccorso, Leticia Banuelos, Ethan Dieringer, Jennifer Lenahan, Emily Spence Davizon, Ellyn P Marder, Jocelyn Mullins, Meagan Kay, Eric J Chow, Sandra J Valenciano, John Lynch, Vanessa Makarewicz, Chloe Bryson-Cahn, Jennifer Hernandez, Kyla Haggith, Valicia Linn, Alex L Greninger, Stephanie Goya, Sierra Gulla, Jennifer Young, Sierra Kerns-Funk, Brianna da Silva Bhatia, Hollianne Bruce, Krista Kniss, Katie Reinhart, Rachel Ohlstein, Shannon Johnson, Christina Schofield, Patrick Smith, Amber Itle, Maura Gibson, Brandi Torrevillas, Azeza Falghoush, Thomas B Waltzek, Kevin Snekvik, Mia Torchetti, Timothy M Uyeki, Scott Lindquist
- PMID: 42096351
- PMCID: PMC13152192
- DOI: 10.15585/mmwr.mm7517a2
Clade 2.3.4.4b influenza A(H5N1) viruses have circulated across migratory bird flyways in the United States since 2022, including in Washington, where backyard flock detections have been reported annually. In November 2025, a Washington resident died from acute respiratory failure after receiving a positive influenza A(H5) test result at a hospital laboratory. Washington Public Health Laboratories confirmed influenza A(H5), and genomic sequencing identified influenza A(H5N5) virus (A6 genotype). Polymerase chain reaction testing detected highly pathogenic avian influenza A(H5) virus clade 2.3.4.4b from an apparently healthy backyard flock of ducks and sediment from a watering basin on the patient's property. Six of eight gene segments from the environmental sample and one duck sample (partial neuraminidase segment) were highly genetically similar to the patient's virus sequence. Although existing wild bird surveillance had not detected influenza A(H5N5) virus (A6) in the U.S. Pacific Flyway, introduction via wild birds into the environment of the backyard flock was likely the source of the patient's exposure. The public health investigation identified approximately 135 exposed persons; symptom monitoring and influenza testing detected no additional cases. The overall risk for avian influenza A remains low among the general U.S. population; however, novel avian influenza A virus infection should be considered in persons with symptoms of influenza and potential exposures.