South Africa has now increased its lockdown restrictions in an attempt to curb the spread of a new Covid-19 variant, which has now been detected in five provinces, and could begin to dominate the country’s epidemic.
The Delta variant — which was initially detected in South Africa in May — is, so far, the most transmissible form of the SARS-CoV-2 virus (the virus that causes Covid-19) in the world, meaning it is able to spread much more efficiently from person to person than other variants.
Here’s what you need to know about the variant.
What is a variant?
Over time viruses undergo small changes in their structure, known as mutations. These are largely insignificant and mostly don’t alter the behaviour of the bug. But occasionally, mutations can affect the way a virus interacts with our bodies and, in turn, change the trajectory of an outbreak.
Scientists use a technique called genomic surveillance to analyse the mutations and understand what they mean for the virus’s behaviour. In South Africa, there is a network of scientists who have been doing just this since March last year. They unravel the genetic code of the versions of the SARS-CoV-2 virus spreading in the country to establish if new variants have emerged.
For SARS-CoV-2, the World Health Organisation (WHO) has come up with two categories of variants that pose a greater public health risk: variants of interest and variants of concern.
A variant of interest is a version of the virus which causes community transmission or has been detected in multiple countries. Variants can also be assigned to this category based on a WHO assessment.
Once the variant has been identified as of interest, its status can then change to a variant of concern if it is shown to have increased transmissibility, cause more severe disease or if it makes treatments, vaccines or diagnostic tools (tests) less effective.
The Delta variant was initially identified as a variant of interest in April 2021, before being categorised as a variant of concern on 11 May.
What do we know about the Delta variant?
Just more than six months ago, South Africa identified its own variant of concern, called Beta. This variant drove the country’s second wave of infections and quickly became the main form of the virus circulating in the country, making up more than 90% of all new cases.
Since then, the Beta variant has consistently dominated South Africa’s epidemic — until now. Saturday’s announcement raises concerns that the Delta variant is quickly overtaking other forms of the virus in circulation in the country.
Perhaps the most concerning trait of the Delta variant is its ability to spread at a rapid rate.
The variant was first identified in India, where it drove a devastating second wave of Covid-19 infections that peaked in May — with a high of 414 433 new cases on 6 May.
As of 22 June, the Delta variant had spread to 85 countries. Because the variant is still fairly new, scientists are still busy gathering data to fully understand what its mutations mean.
But for now, one thing is clear: this form of the virus spreads exceptionally fast. As a result, the Delta variant causes a steep rise in new cases.
A June Eurosurveillance report found that the reproductive number (how many other people one infected person can infect) had increased for all variants of concern. This increase varied depending on the variant, from 25% for the Beta and up to 97% for Delta.
When compared to other variants, the Delta ranges from 30% to 60% more transmissible. Because of this, the report estimates that the Delta variant “is expected to rapidly outcompete other variants and become the dominant circulating lineage [globally] over the coming months”.
This has already been seen in the UK, where the Alpha variant was first identified last year. Public Health England, which falls under the UK’s health department, began investigating the Delta variant in early April when there were just more than 200 cases in the country. Three months later, the variant accounts for almost 95% of cases sequenced in the country.
Can the Delta variant cause more severe disease?
The short answer: it’s too soon to tell.