As the pandemic continues - variants have become the latest concern
with notable examples detected in South Africa,
Brazil and the UK.
But variants are complicated.
Each one is made up of a collection of mutations,
all of which have the potential to change the SARS-CoV-2 virus in unexpected ways.
So what do scientists mean when they talk about variants
and what might this mean for the future of the pandemic?
Viruses multiply by copying their genomes over and over.
But like an old photocopier, these copies aren’t always perfect.
Each of these imperfect copies is a variant.
Normally the imperfections or mutations don’t change how the virus behaves
and they can often make it less successful than the original strain.
But very rarely mutations can change the virus in some important ways.
It could become more infectious, or more able to avoid the immune system.
The more a virus is allowed to replicate unchecked,
the more chance it has to accumulate these rare beneficial mutations.
That can occur when viruses are allowed to spread quickly through a population,
or if they encounter a host that’s less able to fight them,
such as people with compromised immune systems from medical treatment
or those who are HIV+.
If a particular set of mutations makes a variant more successful,
it might become more prominent than others
and that’s when it gets noticed.
Epidemiologists may even decide to label it a ‘variant of concern’,
like the examples identified in Brazil, South Africa and the UK.
For months, scientists have been striving to work out
what’s changed in these variants, and what those changes mean.
Because a variant spreading doesn’t necessarily mean
that it has an advantageous mutation.
For example a small number of people could, by chance,
move a variant from one region to another,
like tourists travelling back from popular vacation spots.
This could cause that variant to start spreading in a new location
even though there may be no significant change to the biology of the virus.
This is called the Founder Effect.
Understanding why a variant has emerged
requires a combination of studies.
Epidemiology can help detect and trace new variants
and flag new or worrying patterns of infection.
Meanwhile lab studies can start to pinpoint
how the mutations are changing the properties of the virus.
And studies like these are starting to identify mutations
that have given the virus an upper hand.
Some variants are faster spreading, and there are hints that certain mutations
could start to weaken or even evade natural and vaccine derived immunity.
For example, the D614G mutation, known to virologists as Doug, spread widely
in the early days of the pandemic and can be seen in almost all variants.
It affects the spike protein
that coronavirus particles use to penetrate cells.
A mutation in the genome changes one amino acid for another,
and makes the new variant more infectious than the original virus.
N501Y also known as Nelly, is another spike protein mutation
which appears to be associated with increased transmissibility.
This mutation has been detected in the B.1.1.7, B.1.351
and P.1 strains – all variants of concern.
The worry of so-called ‘immune escape’ has also been hinted at
with another spike protein mutation, E484K or Eek.
Eek has been spotted in B.1.351 and P.1,
the variants detected in South Africa and Brazil.
Lab studies in early in 2021 showed that the variant could evade
some virus-blocking antibodies,
while trials in South Africa suggested
that the variant reduced the efficacy of several vaccines.
Despite these worries, the coronavirus is actually mutating very slowly
compared to something like influenza
and it seems like the vaccines developed so far
will remain at least partly effective.
But scientists are still taking the threat posed by variants seriously.
And there are several things that can be done to help tackle it.
Firstly, to do anything researchers need data.
It’s very important to monitor and trace the emergence of variants
and that isn’t always simple to do.
Organisations like the COVID-19 Genomics UK consortium, or COG-UK,
have stepped up their efforts to combine fast sequencing
with efficient data sharing.
COG-UK has already sequenced over 400,000 SARS-CoV-2 genomes.
Next, researchers need to look forward to how these mutated viruses
could affect global vaccination efforts.
Existing vaccines can be redesigned
and combinations of vaccines are also being tested
but it could be difficult to perform reliable clinical trials
amid the ongoing vaccination programmes.
Right now though, work needs to continue at a national level.
Public health policies such as track and trace,
social distancing and vaccine roll-outs
are powerful tools to interrupt transmission
and keep tabs on new variants.
After all, every time the virus is prevented from spreading,
it's also prevented from mutating,
nipping new variants in the bud before they even have a chance to develop.