Viral infection and transmission in a large, well-traced outbreak caused by the SARS-CoV-2 Delta variant

The SARS-CoV-2 Delta variant has spread rapidly worldwide. To provide data on its virological profile, we here report the first local transmission of Delta in mainland China. All 167 infections could be traced back to the first index case. Daily sequential PCR testing of quarantined individuals indicated that the viral loads of Delta infections, when they first become PCR-positive, were on average ~1000 times greater compared to lineage A/B infections during the first epidemic wave in China in early 2020, suggesting potentially faster viral replication and greater infectiousness of Delta during early infection. The estimated transmission bottleneck size of the Delta variant was generally narrow, with 1-3…

• CA
  Chinese Academy of Medical Sciences
• NI
  National Institutes of Health
• MR
  Medical Research Council

  Awards: MR/R015600/1, MC_PC_19012
• SP
  Special Project for Research and Development in Key areas of Guangdong Province

  Award: 2019B111103001