The U.S. has confirmed its first-ever case of the rare H5N5 strain of avian influenza, with a Washington resident hospitalized after contracting the virus. The Washington State Department of Health (DOH) confirmed that the individual, who is described as an older adult with underlying health conditions, is the first known person in the United States to have been infected with the H5N5 strain, which has previously been reported in animals but not in humans. The patient reported flu-like symptoms in early November and remains hospitalized as the health authorities investigate the source of the infection.
DOH officials have emphasized that while there are ongoing public health concerns about avian influenza, there is currently no increased risk of the virus spreading to the general public. They noted that human-to-human transmission of avian influenza is extremely rare and has never been documented in the United States. Health experts have also noted that the H5N5 strain, though closely related to the more well-known H5N1 strain, has a different genetic structure and is primarily found in birds, where it has not previously caused illness in humans.
The outbreak in Washington comes as bird flu cases have been on the rise in recent months, with the CDC declaring a bird flu emergency in early 2024 before deactivating it in July. The agency cited declining animal infections and a lack of human cases since February as reasons for ending the emergency. However, the recent H5N5 case suggests that the virus remains a potential public health concern, and health officials continue to urge caution among poultry owners, wildlife handlers, and others who may be in contact with birds.
Public safety measures include avoiding contact with sick or dead birds, using appropriate protective equipment, and reporting any sick wildlife or domestic animals to the Washington State Department of Agriculture (WSDA). Additionally, officials have reminded the public that while the seasonal flu vaccine does not prevent bird flu infections, it may help reduce the risk of a potentially more transmissible variant emerging from the interaction of avian and human influenza viruses.
Health experts continue to monitor the situation closely, as the H5N5 strain could pose a risk if it mutates to become more contagious among humans. The ongoing investigation seeks to determine the exact source of the patient’s infection, which is believed to have originated from a mixed backyard flock of domestic poultry that had exposure to wild birds. These findings underscore the importance of continued vigilance and preventive measures to minimize the spread of avian influenza and mitigate potential public health threats.