The first recorded human death from the H5N5 strain of bird flu has been confirmed in the United States, marking a significant and tragic development in the story of avian influenza.
What We Know About The Case
In early November, an older resident of Grays Harbor County, located on the southwest Pacific coast of Washington state roughly 100 miles from Seattle, became severely ill. The individual, who had underlying health conditions, developed intense flu-like symptoms including a high fever, respiratory distress, and confusion.
After being admitted to hospital, tests confirmed on November 14 that the patient was infected with an H5N5 avian influenza virus. Despite receiving hospital treatment, the patient sadly died on November 21.
Understanding the H5N5 Virus
So, what exactly is the H5N5 influenza virus? Like the more widely known H5N1, it is a type of avian influenza A virus that primarily infects birds. It is classified as a high pathogenicity strain, meaning it causes severe disease in poultry.
The name stems from the two proteins on the virus's surface: haemagglutinin (H) and neuraminidase (N). While this H5N5 shares the H5 subtype with H5N1, its N protein is a different subtype, making it a distinct virus.
While H5N5 is found in wild birds globally and sometimes jumps to poultry flocks, this incident is the first time it has been known to infect a human. The patient kept a backyard poultry flock that had exposure to wild birds, which is the suspected source of the infection.
Assessing the Risk and Response
The immediate question for public health officials is: how concerned should we be? Currently, the wider risk to humans from H5N5 is assessed as low.
There is no evidence of person-to-person transmission in this case, which is a critical warning sign scientists monitor. The vast majority of such spillover infections from birds to humans are one-off events.
However, this tragic case underscores that avian influenza viruses remain a potential source of future pandemics. The response focuses on controlling the virus in bird populations through surveillance, farm biosecurity, and, as a last resort, culling. Continuous and careful monitoring of these viruses is essential to global health security.
