A resident of Washington state has been diagnosed with a human infection of the H5N5 bird flu virus, according to state health officials. This case is notable as it represents the first confirmed human infection of this particular strain in the United States since February. The individual, an older adult with pre-existing health conditions, is currently hospitalized. Preliminary findings were announced on Thursday, with confirmation following on Friday.

The H5N5 strain is distinct from the H5N1 virus, which has been associated with a significant number of human infections in the U.S. in recent years. Health officials have indicated that the H5N5 strain does not appear to pose a greater risk to human health compared to H5N1, which has resulted in approximately 70 reported human cases in 2024 and 2025, most of which were mild and occurred among workers in the dairy and poultry industries.

Richard Webby, a flu researcher at St. Jude Children’s Research Hospital, noted that the two viruses behave similarly from a health perspective. The Centers for Disease Control and Prevention (CDC) echoed this sentiment, stating that there is no evidence to suggest an increased public health risk due to this case.

The infected individual has a backyard flock of domestic poultry that had contact with wild birds, which is believed to be the likely source of exposure. Investigations are ongoing to determine the exact circumstances surrounding the infection. The CDC is also awaiting further specimens from Washington for additional testing to better understand the implications of the H5N5 strain.