The Delta variant is 50% more transmissible than the Alpha variant, first discovered in the UK, experts from the National Centre for Disease Control (NCDC) and the CSIR Institute of Genomics and Integrative Biology (IGIB) said.
The rapid surge in cases during Delhi’s fourth Covid-19 wave was mainly driven by the Delta variant, which likely has immune-evasion properties and accounted for 60 per cent of the cases in April, according to a new study.
The Delta variant, B.1.617.2, is 50 per cent more transmissible than the Alpha variant, B1.117, first discovered in the UK, say researchers from the National Centre for Disease Control (NCDC) and the CSIR Institute of Genomics and Integrative Biology (IGIB).
Prior infections, high seropositivity and partial vaccination are “insufficient impediments” to the spread of the Delta variant, found the scientists. They traced the factors contributing to the scale and speed of the fourth wave that started in April in Delhi and compared them to the preceding three waves last year.
“We find that this surge of SARS-CoV-2 infections in Delhi is best explained by the introduction of a new highly transmissible variant of concern (VOC), B.1.617.2, with likely immune-evasion properties,” the researchers noted.
The variant may have led to insufficient neutralising immunity in people, despite high seropositivity, and social behaviour may have augmented the surge by promoting transmission, they added.
Neutralising immunity consists of naturally occurring antibodies that play an important role in the immune system.
To determine whether SARS-CoV2 variants may be responsible for the April 2021 outbreak in Delhi, the researchers sequenced and analysed community samples from Delhi from the previous outbreak in November 2020 until May 2021 and related it to effective reproductive numbers (Rt).
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