First Human Case of H5N5 Bird Flu Reported in Washington State

In a concerning development, a resident of Washington state has tested positive for bird flu, marking the first human case in the United States since February and the first involving the H5N5 strain. This case was reported by state health officials last week, highlighting the ongoing challenges posed by avian influenza.

The patient, described as an “older adult” with underlying health conditions, resides in Grays Harbor County on the Olympic Peninsula. They have been hospitalized since early November, exhibiting symptoms such as high fever, confusion, and difficulty breathing. Health officials believe the most likely source of the infection was the individual’s backyard flock of mixed domestic poultry, which had been exposed to wild birds.

The H5N5 strain is a subtype of avian influenza that differs from the more widely recognized H5N1 strain, which has been prevalent among wild birds and poultry globally for several years. According to the U.S. Centers for Disease Control and Prevention (CDC), the distinction between H5N5 and H5N1 lies primarily in a surface protein. Currently, it remains unclear whether this first human case of H5N5 carries broader implications or presents different risks compared to other avian flu viruses.

Each human infection is closely monitored, as it provides the virus an opportunity to mutate in ways that could enhance its transmissibility or severity. A study published in 2024 revealed that a single genetic change in an H5N1 virus could shift its receptor binding preference from birds to humans, raising alarms about potential future risks.

Despite the emergence of this case, health agencies maintain that the current risk to the general public remains low. There have been no documented instances of the virus spreading from human to human. Nonetheless, health workers are actively monitoring individuals who had close contact with the patient to ensure prompt detection and response.

In 2025 alone, four human cases of highly pathogenic avian influenza have been reported in the U.S., with 71 total cases since early 2024. Most of these cases involved individuals working in dairy or poultry farming, with one reported death in Louisiana. Fortunately, the majority of cases exhibited mild symptoms.

The spread of bird flu among animals continues to be a significant concern. In the last month, the virus has impacted 86 poultry flocks across the nation, affecting over 1.8 million birds, as reported by the U.S. Department of Agriculture. The virus is particularly prone to spreading when infected wild birds come into contact with commercial operations or backyard flocks.

Washington health officials have noted that the risk of avian influenza typically increases in the fall and winter months when migratory birds pass through the region, potentially introducing the virus to poultry farms and backyard flocks. As this situation develops, vigilance and public awareness remain crucial in managing the risks associated with avian influenza.