H5N1 expert says ‘The virus is definitely mutating’

17 December 2008

Guan Yi, an expert on H5N1 influenza virus, is quoted in China Daily as saying that “The virus is definitely mutating”.

Yi’s comments were in reference to the continuing pandemic of H5N1 influenza in poultry farms. He indicates that some farms are using a vaccine against an American H5N2 strain, which is not likely to be fully protective against the currently circulating H5N1 strains. In the past 10 years, at least 10 strains of the H5N1 virus have been identified, providing the fodder for Dr. Yi’s overly obvious statement.

I find it hard to believe that a virus ‘expert’ would ever make such a statement as ‘the virus is definitely mutating’. Virus genomes continuously undergo mutation, as a consequence of error-prone nucleic acid polymerases. The error rate for RNA virus genomes is phenomenal, because the viral polymerases cannot correct its mistakes. The error rates for viral RNA-dependent RNA polymerases have been estimated to be between 1 in 10,000 to 100,000 nucleotides polymerized. For a virus with a 10 kb genome, a frequency of 1 in 10,000 means that each RNA produced contains at least one mutation. Dr. Yi states the obvious when he says that the H5N1 virus is mutating. The genomes of these viruses are constantly undergoing change, not just in this specific outbreak.

What should Dr. Yi have said? I would have indicated that the rapid change in the antigenic composition of circulating H5N1 strains is likely rendering the vaccine ineffective. Maybe he said that, but was misquoted by the press. These things do happen, right?

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  • sjj

    “The virus is definitely mutating”… i think here you are taking meaning of mutating as Evolving… but even one change in nucleotide is indicated as mutation, i think it is right to say that virus is mutating…

  • gsgs

    we observe ~40 mutations per influenza genome per year or 1 per 350000 nucleotides.
    That's what survives, most mutations could be non-synonymous and disadvantageous
    and die soon, I'm not sure.

    In human flu only a few strains are prevalent per season all others are outcrowded.
    That's why the diversity doesn't really grow much, despite mutation, and why
    the number of required vaccine strains doesn't grow exponentially.

    Now, this number of prevalent strains may grow and that may be meant with
    “definitely mutating”. Maybe define this as M(H5N1,2009) the average antigenic distance
    of two randomny iolated H5N1 viruses in 2009.
    Compare with M(mexflu,2009),M(H3N2,2008),M(H3N8,equine,2009) etc. -
    and draw charts e.g. M(H3N2,human,USA,year) over the years.

  • gsgs

    we observe ~40 mutations per influenza genome per year or 1 per 350000 nucleotides.
    That's what survives, most mutations could be non-synonymous and disadvantageous
    and die soon, I'm not sure.

    In human flu only a few strains are prevalent per season all others are outcrowded.
    That's why the diversity doesn't really grow much, despite mutation, and why
    the number of required vaccine strains doesn't grow exponentially.

    Now, this number of prevalent strains may grow and that may be meant with
    “definitely mutating”. Maybe define this as M(H5N1,2009) the average antigenic distance
    of two randomny iolated H5N1 viruses in 2009.
    Compare with M(mexflu,2009),M(H3N2,2008),M(H3N8,equine,2009) etc. -
    and draw charts e.g. M(H3N2,human,USA,year) over the years.