• Question: How many mutations of the common cold have there been forever? Arthur

    Asked by to Bethany, Hannah, Keith, Peter, Ramya on 19 Jun 2014. This question was also asked by .
    • Photo: Hannah Tanner

      Hannah Tanner answered on 19 Jun 2014:

      So many no-one could every count them! Viruses are mutating all the time. Every time a virus replicates small mistakes can be made in the DNA replication and that’s a mutation. Some mutants don’t survive but some do and may cause a new strain of infection.

      The common cold is not just cause by one “species” of virus there are loads including rhinovirus, adenovirus, enterovirus, bocavirus, coronavirus, parainfuenza virus, influenza virus, respiratory syncytial virus, human metapneumovirus and more!

      This diversity of viruses and mutants of viruses explains why we get colds again and again.

    • Photo: Peter Elliott

      Peter Elliott answered on 19 Jun 2014:

      Hannah has summed it up nicely. When a virus makes a copy of itself it makes mistakes in its RNA. The genome (the blueprints of the cell) is 92,000 bases (ATGC) and each time it replicate itself then one of these bases changes. This could has no effect, a little effect or a big effect on how the next virus behaves.

      If there is a mutation on the compounds that form the outside of the virus then your body’s immune system wont recognise it and it could possibly infect you again. That is why during the course of your life you will catch the common cold on multiple occasions.

    • Photo: Bethany Dearlove

      Bethany Dearlove answered on 23 Jun 2014:

      Hi Arthur!

      Hannah and Peter are right – lots! If we just take the virus that causes most common colds, rhinovirus, then it’s estimated their global population is made up of one billion trillion (thats a 1 with 22 zeros after it) viruses. It’s been estimated that the mutation rate is around 0.0001% of the genome per replication – meaning that on average there will be 1-10 mutations each time the virus is copied. That’s a lot of viruses…and even more mistakes!

      However, I should mention that these are only the mutations we have detected and can count. Some mutations will have distorted the viruses so much they can’t function, and therefore will disappear before we get to sample them. The amount of errors made during copying could actually be even higher!

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