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COVID-19 coronavirus Delta variant Sars ncov 2 2021. Delta plus Strain. Idia Coronavirus delta variant. B.1.617.2 E484Q L452R. 3D illustration

SARS-CoV-2 Delta variant, also known as lineage B.1.617.2, or Indian variant is a variant of lineage B.1.617 of SARS-CoV-2, the virus that causes COVID-19. It was first detected in India in late 2020. The World Health Organization (WHO) named it the Delta variant on 31 May 2021.

It has mutations in the gene encoding the SARS-CoV-2 spike protein causing the substitutions T478K, P681R and L452R, which are known to affect transmissibility of the virus as well as whether it can be neutralised by antibodies for previously circulating variants of the COVID-19 virus. In August 2021, Public Health England (PHE) reported secondary attack rate in household contacts of non-travel or unknown cases for Delta to be 10.8% versus 10.2% for the alpha variant; the case fatality rate for those 300,010 with Delta is 0.2%, where half of the cases and one third of the deaths are unvaccinated. COVID-19 vaccines are effective in preventing severe disease or hospitalisation from infection with the variant.