A quiet alarm has sounded in public health circles. A resident of Grays Harbor County, Washington, has become the first person in the United States confirmed to be infected with the H5N5 strain of avian influenza – a virus previously unseen in humans.
The patient, an older adult with pre-existing health conditions, first exhibited flu-like symptoms earlier in November and remains hospitalized. This marks the nation’s first human case of bird flu diagnosed since February, reigniting concerns about potential viral shifts.
Investigators quickly focused on the patient’s home environment, discovering a mixed flock of domestic poultry that had been exposed to wild birds. This backyard exposure is currently considered the most probable source of the infection, though a thorough investigation is still underway.
What sets this case apart is the specific viral strain: H5N5. While avian influenza viruses are regularly monitored in animal populations, H5N5 had, until now, never been detected in a human. This discovery represents a significant, and potentially unsettling, evolutionary step.
Public health officials are keen to emphasize that, at this time, the risk to the general public remains low. Human-to-human transmission of avian influenza is exceptionally rare, and no such spread has ever been documented within the United States.
However, experts are urging caution. Avoiding contact with sick or deceased birds, utilizing protective gear when handling poultry, and promptly reporting any unusual wildlife or domestic animal illnesses to agricultural authorities are crucial preventative measures.
The seasonal flu vaccine won’t protect against H5N5, but vaccination is still strongly recommended. The reasoning is critical: a co-infection with both human and avian influenza viruses could potentially trigger the emergence of a new strain more easily transmitted between people.
This development arrives after the Centers for Disease Control and Prevention declared the previous H5N1 bird flu emergency officially over in July. That response, activated in 2024, was deactivated due to declining animal infections and a period without human cases.
H5N5 is closely related to H5N1, sharing a significant portion of its genetic makeup. The key difference lies in a structural variation – a change to the virus’s “end piece” – that alters its behavior and characteristics.
While H5N1 has caused human illness and, tragically, fatalities over the years, H5N5 has largely remained confined to bird populations. This new case signals a worrying breach of that barrier, demanding vigilant monitoring and proactive public health strategies.
