An evolving virus
Since it was first identified last year, the virus causing Covid-19 has mutated thousands of times. But while most variants have little effect on the disease, some pose more of a risk.
Strains, variants, mutations: what’s the difference?
All three are words associated with viruses. Strain is the term used to describe Sars-CoV-2. This is the virus that causes Covid-19 and is a member of the coronavirus family. Other coronavirus strains include the common cold and SARS.
Viruses also mutate. These tiny genetic changes happen as the virus makes new copies of itself to spread and thrive. As these mutations take place, new version are created. These are called variants.
Is all this normal?
Yes. All viruses mutate naturally. The virus causing the flu mutates every year, which is why the vaccinations take place annually. Sars-CoV-2 is no exception. It has been mutating constantly since it was first identified early last year. Experts estimate that the virus accumulates around two changes each month.
Mutations are usually a chance event that will have little impact on the properties of a virus. Pathogen expert Dr Lucy van Dorp says: “The very vast majority of mutations… are there as passengers.” In other words, they do not change how the virus behaves – they are just carried along.
So, what’s the worry?
Because, every once in a while, a virus strikes lucky by mutating in a way that positively affects its ability to survive and reproduce. Viruses with these mutations can become more infectious or threatening to the humans they affect.
There are now many thousands of different variants of the pandemic virus circulating. But a small number of those have developed mutations that have caused concern. In November, one variant referred to as Cluster 5 started spreading rapidly through mink farms in Denmark. Officials ordered a strict local lockdown and a mass cull of the animals.
Why are variants in the news again?
At the end of last year, two further variants emerged that have caused experts to worry. The first, VOC202012/01, was detected in Kent. The other, 501.V2 emerged in South Africa. They are unrelated, but both appear to be much more contagious than previous variants.
This is a problem because tougher restrictions on society may be needed to control the spread. The Kent variant has now been detected in over 20 countries – and the sharp increase in cases has sent all four UK nations into another lockdown.
Is the problem just that they spread quickly?
No. The Sars-CoV-2 virus is studded with proteins that it uses to enter human cells. These so-called spike proteins are key to the success of vaccines. The Oxford-AstraZeneca vaccine introduces the proteins’ genetic information into the body’s cells, training the immune system to fight off any future infection. Meanwhile, the mRNA vaccine developed by Pfizer uses new technology to encourage the body itself to recreate and learn to fight the spike protein.
One of the main reasons experts are so concerned about the Kent and South African variants is because they have mutations affecting – and therefore potentially changing – the spike protein.
Does that mean the vaccines will stop working?
Not to worry! Most experts agree that the mutations on the Kent variant do not cause sufficient changes to affect the vaccines. Plus, there is no evidence to suggest that either variant causes more serious illness.
According to the virologists, one mutation found in the South African variant causes more significant changes to the spike protein. But even in the worst case scenario, now that we have the vaccines, they can be redesigned and tweaked to be a better match in a matter of weeks.
- Should vaccination against Covid-19 be made compulsory?
- Create your own infographic about the Sars-CoV-2 virus. Include five important facts as well as a diagram, indicating the protein spikes.
- Though many people refer to it in short as a virus, Covid-19 is actually the disease caused when somebody is infected with Sars-CoV-2.
- Severe Acute Respiratory Syndrome is a viral respiratory disease. It was first identified in 2003 in China, and spread to four other countries.
- A micro-organism that causes disease, like a bacterium or virus.
- The slaughter of a group of animals, either to control population numbers or in the case of disease. A 2001 outbreak of foot-and-mouth disease in 2001 led to the culling of millions of cows and sheep.
- The letters stand for “virus of concern”. When first identified, it was named VUI202012/01 for “virus under investigation”.
- By 2 January, the variant had been detected in the UK, Japan, Australia, Zambia, France and South Korea.
- The vaccine was developed by a team made up of scientists at Oxford University, partnered with the Swedish-British company.
- Messenger RNA is a copy of a DNA strand, used in the process of synthesising proteins. When used in a vaccine, it encourages human cells to produce harmless versions of the protein spikes on the outside of a virus cell, allowing the immune system to produce defences against them, and against the virus itself.
- Medical researchers or scientists who study viruses and the diseases caused by them.
- The mutation, called E484K, has been shown to reduce some antibody recognition – meaning that the variant carrying the mutation could bypass immune protection from current vaccines or prior infection.