What is the delta version of Covid-19, and why is it a concern in India?
Several SARS-CoV-2 variants are circulating globally. One of these is the B.1.617 lineage, which was discovered in India earlier this year. What is the delta version of COVID-19, and what makes it a type of concern?
In its latest risk assessment for the SARS-C0V-2 variant, Public Health England (PHE) has stated that 61% of the sequenced samples now belong to the delta variant (B.1.617.2). This means that the Delta variant, which was first discovered in India, is more impressive in the UK than the Alpha variant, which made a surge in the UK last year.
What is the delta version of COVID-19?
Several SARS-CoV-2 variants are circulating globally. One of these is the B.1.617 lineage, which was discovered in India earlier this year. Preliminary evidence suggests that it’s sub-lineage b.1.617.2, known as the delta variant, is more transmissible than contemporary lineages.
The World Health Organization (WHO), which has given it the delta label, has classified it as a type of concern (VOC). It said it continues to observe “significantly increased communicability” and “an increasing number of countries reporting such associated outbreaks”.
WHO classifies a variant as a VOC when it is associated with increased transmission efficiency or harmful changes in the Covid-19 epidemiology; increase in the virus; or lack of effectiveness of public health measures or available diagnostics, vaccines, therapeutics.
What Makes the Delta Version a VOC?
The different forms are characterized by mutations – or changes in the genetic material of the virus. An RNA virus, such as SARS-CoV-2, is made up of about 30,000 base pairs of amino acids, placed next to each other like bricks.
A change in any of these bases causes a mutation, which effectively changes the shape and behavior of the virus. The delta variant contains multiple mutations in the spike protein. At least four mutations are significant.
One of these is called L452R, which was first reported in Denmark in March last year. This mutation is more transmissible than wild-type strains and is also associated with lower antibody efficacy and lower neutralization by vaccine sera.
The mutation P681R is linked to chemical processes that can increase transmissibility, PHE says.
The D614G mutation was first documented in the Americas at the start of the epidemic, which was initially transmitted to Europe. “There is evidence that variations with this mutation spread more quickly,” the Centers for Disease Prevention and Control (CDC) says.
Another mutation in delta is T478K. This variant was present in about 65% of events in B.1.1.222, first detected in Mexico last year and associated with high infectivity.
What is the evidence on communicability so far?
Public Health England said Delta continues to demonstrate a significantly higher growth rate than Alpha in multiple analyses. In the week starting 17 May, a PHE analysis of genome sequencing data in the UK found 61% of cases to be delta.
Delta cases are increasing while alpha cases are decreasing. In addition, PHE said, the secondary attack rate has been higher for Delta than for Alpha.
What is the evidence on seriousness?
PHE said early evidence from England and Scotland suggests “there may be an increased risk of hospitalization compared to contemporary alpha cases”. “A large number of cases are still within the follow-up period. In some areas, hospital admissions show early signs of increasing, but the national trend is unclear,” it said.
How dangerous is Delta variant?
“The Delta variant is currently the greatest threat in the U.S. to our attempt to eliminate COVID-19,” Fauci said. The variant, first identified in India, is the most contagious yet and, among those not yet vaccinated, may trigger serious illness in more people than other variants do, he said.