Two recently-discovered strains of coronavirus, which a study has suggested to be effective at evading immunity from previous infections, have sparked fears in the United States of another wave.
BA.4 and BA.5, sub-variants of the Omicron variant of coronavirus, were first discovered in South Africa, where they are now driving a surge in infections. The positivity rate has touched 22 per cent in the country and health experts there have said the country is likely in its fifth Covid-19 wave.
While earlier strains, such as Delta and Omicron variants and their sub-variants, could also evade immunity, the thing about BA.4 and BA.5 is that they are said to be even more transmissible than the “stealth Omicron” – BA.2, which was itself 80 per cent more transmissible than the original Omicron strain.
Here in this piece, we will explain all about variants and sub-variants or coronavirus and what risks these two recently-discovered strains pose.
What variants and sub-variants?
The Covid-19 disease is caused by a kind of coronavirus known as SARS-Cov-2. This virus, like all viruses, evolves over time and acquires mutations, leading to the creation of variants, which may be understood as different versions of the virus.
These variants further evolve and split into different drains, leading sub-variants. The Delta variant, which drove India deadly second Covid-19 wave, has up to 200 sub-variants.
These mutations and resultant variants and sub-variants in itself are not a cause of concern. Some of these mutations, however, make the virus more transmissible – as in case of Omicron – or more deadly – as in case of Delta. It is these mutations (and resultant variants and sub-variants) that are a cause of concern.
Besides BA.4 and BA.5, other Omicron sub-variants BA.2, XE, BA.2.12 and BA.2.12.1, have raised concerns.
How different are BA.4 and BA.5 from earlier strains?
The BA.4 and BA.5 sub-variants are more similar to the original Omicron strain, which means they have undergone greater mutations than close predecessors BA.2 and BA.3.
South African Covid-19 expert Tulio de Oliveira, the head of the institutes at the universities of KwaZulu-Natal and Stellenbosch, told Bloomberg that these two sub-variants have mutations that allow them to evade immunity from previous infections and some vaccines.
More than 90 per cent of people have some sort of immunity in South Africa, as per experts.
In the United States, only around 66 per cent people are fully vaccinated. Concerns have therefore risen about these variants that can bypass previous immunity.
How severe are they and should you be concerned?
South African health officials said last week that hospitalisations are rising from infections fuelled by these two variants. However, deaths have not yet spiked, but experts told Bloomberg that deaths are considered a “lagging indicator”, which means that the effect on deaths will be known after some time.
Professor Alex Sigal of Africa Health Research Institute in South Africa told Fortune that while a wave is “a strong possibility”, it will not be a huge one as people still have immunity against Omicron and that should hold off the severity – even if with reduced efficiency.
“Infections? Yes Disease severity? Not so much,” said Sigal on the question of increase in infections and severity.
Sigal, who is one of the authors of the study that found these strains’ immunity-evading features, said sub-variants are not very different from each other, so their waves are not that severe as well.
He said, “When I see something completely different, that’s when it’s time to really get concerned.”
However, even if these new sub-variants don’t cause severe disease, they certainly can cause new waves of infection which was until recently thought to be possible only with new variants (not sub-variants), noted Sigal.