Amid Bird Flu concerns, US reports its first human H5N5 death

The United States has reported its first human death caused by the H5N5 bird flu strain. Learn what this development means and how it impacts ongoing health concerns.

The United States has recorded its first human death from the rare bird-flu strain H5N5, a major development in global public-health monitoring. The person, an older adult with underlying health conditions, was admitted to hospital in early November after developing flu-like symptoms, including high fever, respiratory trouble and confusion.

Laboratory tests at the University of Washington identified the virus subtype as H5N5. The result was later confirmed by the Centers for Disease Control and Prevention (CDC), marking this as the first ever confirmed human H5N5 case worldwide.

What does the new research show?

Recent international research, led by scientists from prominent universities, suggests that bird-flu viruses like H5N5 may be able to survive and reproduce even at the higher body temperatures associated with fever. This is a worrying insight because fever is usually the immune system’s natural defense against viruses.

In experiments using animal models, researchers observed that while typical human influenza viruses are impaired by fever-level temperatures, avian influenza viruses often remain resilient. The difference seems to stem from a gene variant, the virus’s so-called “temperature-sensitivity gene” which may make bird flu able to withstand conditions that would normally suppress human flu viruses.

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This ability of avian flu viruses to thrive at higher temperatures could partly explain why they can cause more severe illness, especially if they infect the lungs or lower respiratory tract, where the internal temperature aligns more with fever-level heat.

The risk and response

Despite the tragic outcome, health officials say the risk to the general public remains low at present. There is no evidence of human-to-human transmission in this case. Close contacts and others who may have been exposed to the infected person or their bird flock are being monitored for symptoms.

Still, experts caution that this case serves as a reminder: avian flu viruses can evolve, adapt, and in rare cases infect humans. Monitoring wildlife, domestic birds, and backyard poultry flocks remains crucial for early detection and prevention of potential outbreaks.

What makes H5N5 different from common flu strains?

H5N5 is an avian-origin influenza virus, typically found in birds rather than mammals or humans. Much like the better-known H5N1 strain, it is considered highly pathogenic, capable of causing severe disease in bird populations, which makes any rare transmission to humans a significant concern. Adding to this worry is the virus’s unusual temperature resilience, unlike many human flu viruses that weaken when body temperature rises, avian flu viruses such as H5N5 can remain stable even during fever, potentially reducing the body’s natural ability to fight the infection.