How are Covid-19 variants classified and named?

Omicron, the latest coronavirus variant detected in southern Africa, has sparked further concern that more transmissible and deadly forms of the virus may make it more difficult to control the pandemic.

The strain has been named as a Variant of Concern by the World Health Organisation, leading to the introduction of travel bans aimed at curbing its transmission.

While Omicron, also known as B.1.1.529, has mostly been found in one province of South Africa, it has spread more widely, including to Europe.

Particularly worrying is its large number of mutations: 50 in total, of which more than 30 are on the spike protein, which attaches to human cells.

Almost two years on from when the coronavirus was first reported, ideas about mutations and variants are familiar to the public. Here, The National looks at how variants are identified and named.

Q Why do variants develop?

A Each time the virus copies its genetic material (ribonucleic acid or RNA), something it has to do to replicate, there is a risk that mistakes or mutations will happen.

Some result in the virus incorporating different amino acids (protein building blocks) into the proteins that it makes.

These may alter how the virus behaves, such as influencing how easily it spreads from one person to another, or the extent to which it evades protection from vaccines.

Mutations that benefit the virus are likely to become more common and, together with others, may form a collection of changes characteristic of a new variant.

Health authorities around the globe constantly test samples of the virus to track genetic changes and identify when such variants have been created.

How are variants classified?

The WHO tracks Variants of Concern (VOC), Variants of Interest (VOI), variants under monitoring (VUM) and formerly monitored variants.

The European Centre for Disease Prevention and Control uses a similar system, although instead of formerly monitored variants, it has a category of de-escalated variants.

Three things characterise VOC: they are more transmissible, can evade the protection from vaccines and cause more severe disease or are resistant to treatment.

In May, the WHO introduced a VOC and VOI naming system based on the Greek alphabet to end the “stigmatising and discriminatory” practice of identifying them by the place where they were first identified.

The WHO currently has five VOC: Alpha (first identified in the UK), Beta (South Africa), Gamma (Brazil), Delta (India) and Omicron (several countries).

There are two VOI, Lambda (first identified in Peru) and Mu (Colombia). Variants in this category have genetic changes that may make them fit the criteria for VOC and are also spreading widely.

With VUM, there are genetic changes that are concerning and may pose a risk, but more evidence is needed.

When VOC or VOI are found to no longer pose a major public health risk, they may be reclassified as formerly monitored variants.

Why is classifying variants useful?

The WHO says the work that it and many other health authorities do to monitor how the virus is changing can help spread the message about changes needed to respond to new variants.

Governments may introduce travel bans or other restrictions to prevent the spread of variants.

Prof John Oxford, emeritus professor of virology at Queen Mary, University of London, said he was “very impressed” by the molecular diagnostic tools used to monitor how the coronavirus was evolving and spreading.

When he was carrying out work with influenza in the past, he said scientists “would have loved” to have had the tests that are now available.

“It’s head and shoulders above what we were able to do with the flu,” he said.

He said people should not overreact to the latest variant.

“We have to sit tight and see if it’s more virulent and more spreadable,” he said.

“It’s easy to get a society in a flap. We have to be a bit more relaxed until we’re sure.”