Bird flu: One mutation is all that remains before the H5N1 virus spreads from human to human

Sub : Sci

Sec: Health

Context:

The H5N1 avian influenza virus is one mutation away from becoming infectious to humans, enabling it to spread from one person to another, scientists have revealed.

Background:

H5N1 Strain: The clade 2.3.4.4b strain of H5N1, widespread among poultry, wild birds, and mammals, has triggered a global epizootic event.
Current Human Infections: While no human-to-human transmission has been confirmed, 58 humans have contracted the virus from dairy cattle and poultry exposure in the U.S. this year.

Findings:

Mutation Discovery: Researchers from Scripps Research identified a mutation, Gln226Leu (Q226L), in hemagglutinin protein from a cow in Texas. This mutation significantly enhances the virus’s ability to bind to human-like glycan receptors, increasing its potential infectivity.
Single Mutation Concern: Historically, at least three mutations were needed for avian flu viruses to adapt to humans. Now, just one mutation shows significant adaptability.
Additional Mutation: The Asn224Lys mutation was found to further stabilize the virus’s hold on human cells.
Other Contributing Mutations: Genetic changes such as PB2-E627K, which enhance viral replication in human cells, may still be necessary for sustained human-to-human transmission.

Implications:

Pandemic Risk: The WHO has warned of a 52% fatality rate for bird flu and urged enhanced surveillance in poultry and wild birds to monitor mutations.
Potential Adaptation Pathways: The study echoes historical patterns seen in past influenza pandemics (1918, 1957, 1968, and 2009), where receptor-binding switches played a key role.
Experimental Observations: In ferret studies, PB2-E627K mutations facilitated airborne transmission. Similar mutations have been observed in human infections in Canada.

Current Assessment:

Risk to Humans: The CDC currently classifies the risk of human-to-human H5N1 transmission as low. However, increasing animal-to-human cases and adaptive mutations warrant vigilance.
Challenges: The virus’s ability to bind human glycan receptors alone is insufficient for efficient transmission; additional mutations are required to stabilize and replicate in human hosts.

Scientific Outlook:

Surveillance and Research: Experts call for enhanced monitoring of viral mutations in infected animals and humans.
Precautionary Measures: Mitigating high viral concentrations in environments such as poultry farms and cattle herds is critical.
Policy Implications: Strengthening biosecurity measures and pandemic preparedness plans remains crucial to prevent a potential crisis.

Source: DTE