Genomic characterization and epidemiology of an emerging SARS-CoV-2 variant in Delhi, India

Science. 2021 Nov 19;374(6570):995-999. doi: 10.1126/science.abj9932. Epub 2021 Oct 14.

Abstract

Delhi, the national capital of India, experienced multiple severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreaks in 2020 and reached population seropositivity of >50% by 2021. During April 2021, the city became overwhelmed by COVID-19 cases and fatalities, as a new variant, B.1.617.2 (Delta), replaced B.1.1.7 (Alpha). A Bayesian model explains the growth advantage of Delta through a combination of increased transmissibility and reduced sensitivity to immune responses generated against earlier variants (median estimates: 1.5-fold greater transmissibility and 20% reduction in sensitivity). Seropositivity of an employee and family cohort increased from 42% to 87.5% between March and July 2021, with 27% reinfections, as judged by increased antibody concentration after a previous decline. The likely high transmissibility and partial evasion of immunity by the Delta variant contributed to an overwhelming surge in Delhi.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • COVID-19 / epidemiology*
  • COVID-19 / immunology
  • COVID-19 / transmission
  • COVID-19 / virology*
  • Child
  • Genome, Viral*
  • Humans
  • Immune Evasion
  • India / epidemiology
  • Molecular Epidemiology
  • Phylogeny
  • Reinfection
  • Seroepidemiologic Studies
  • Young Adult