Avian flu: «for whom the bell tolls»?

Area of Science:

• Virology
• Epidemiology
• Public Health

Background:

• The Orthomyxoviridae family includes avian influenza viruses, with H5 and H7 subtypes known for high virulence (HPAI) causing significant mortality in domestic birds.
• Highly virulent avian influenza virus H5, identified over a century ago, has caused widespread outbreaks in birds globally, with limited human cases.
• Recent H5N1 outbreaks (clade h2.3.4.4b) in birds are increasing, with notable transmission to diverse mammal species.

Purpose of the Study:

• To analyze the current global spread of highly virulent H5N1 avian influenza.
• To investigate the implications of increased mammalian transmission and potential human adaptation.
• To assess the pandemic threat posed by H5N1 avian influenza.

Main Methods:

• Review of global avian influenza surveillance data.
• Analysis of genetic sequences from H5N1 strains isolated from birds and mammals.
• Epidemiological assessment of interspecies transmission events.

Main Results:

• Global H5N1 avian influenza outbreaks have caused nearly 1 billion bird deaths.
• Increased mortality events observed in various mammal species, including seals, sea lions, minks, and cats.
• H5N1 strains from mammals exhibit genetic markers (PB2, NP, HA, NA genes) suggesting partial adaptation for human transmission.

Conclusions:

• The current H5N1 avian influenza situation represents a significant global health threat.
• Mammals may serve as critical intermediate hosts for viral adaptation, increasing the risk of human spillover.
• Pre-adapted H5N1 strains transitioning to humans could lead to catastrophic pandemic consequences.