SARS-CoV-2 variant Delta rapidly displaced variant Alpha in the United States and led to higher viral loads

• Published in: Cell reports. Medicine 2022-03, Vol.3 (3), p.100564-100564, Article 100564
• Main Authors: Bolze, Alexandre, Luo, Shishi, White, Simon, Cirulli, Elizabeth T., Wyman, Dana, Dei Rossi, Andrew, Machado, Henrique, Cassens, Tyler, Jacobs, Sharoni, Schiabor Barrett, Kelly M., Tanudjaja, Francisco, Tsan, Kevin, Nguyen, Jason, Ramirez, Jimmy M., Sandoval, Efren, Wang, Xueqing, Wong, David, Becker, David, Laurent, Marc, Lu, James T., Isaksson, Magnus, Washington, Nicole L., Lee, William
• Format: Article
• Language: English
• Subjects: Alpha; COVID-19; COVID-19 - epidemiology; Delta; Gamma; Humans; Iota; SARS-CoV-2; SARS-CoV-2 - genetics; surveillance; transmissibility; United States - epidemiology; viral load; Viral Load - genetics
• ISSN: 2666-3791; 2666-3791
• DOI: 10.1016/j.xcrm.2022.100564

We report on the sequencing of 74,348 SARS-CoV-2 positive samples collected across the United States and show that the Delta variant, first detected in the United States in March 2021, made up the majority of SARS-CoV-2 infections by July 1, 2021 and accounted for >99.9% of the infections by September 2021. Not only did Delta displace variant Alpha, which was the dominant variant at the time, it also displaced the Gamma, Iota, and Mu variants. Through an analysis of quantification cycle (Cq) values, we demonstrate that Delta infections tend to have a 1.7× higher viral load compared to Alpha infections (a decrease of 0.8 Cq) on average. Our results are consistent with the hypothesis that the increased transmissibility of the Delta variant could be due to the ability of the Delta variant to establish a higher viral load earlier in the infection as compared to the Alpha variant. [Display omitted] •Alpha was dominant in spring 2021 and went extinct in fall 2021 in the United States•Delta also displaced Gamma, Iota, and Mu variants•On average, viral load was ∼1.7× higher in Delta infections versus Alpha infections Bolze et al. show that the Delta variant of SARS-CoV-2 rapidly grew to become the dominant variant by July 2021 in the United States. Delta displaced variants of concern Alpha and Gamma and the variants of interest Iota and Mu.