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Volume 29, Number 10—October 2023
Research

Cycle Threshold Values as Indication of Increasing SARS-CoV-2 New Variants, England, 2020–2022

Rebecca E. HarrisonComments to Author , Ahmed Hamada, Nujcharee Haswell, Aigul Groves, Karina-Doris Vihta, Kerry Cella, Sarah Garner, Ann Sarah Walker, and Anna C. Seale
Author affiliations: United Kingdom Health Security Agency, London, UK (R.E. Harrison, A. Hamada, N. Haswell, A. Groves, K. Cella, S. Garner, A.C. Seale); University of Oxford, Oxford, UK (K.-D. Vihta, A.S. Walker); Warwick Medical School, University of Warwick, Coventry, UK (A.C. Seale); London School of Hygiene & Tropical Medicine, London (A.C. Seale)

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Figure 4

Emergence of novel Delta variant of SARS CoV-2 in England, showing mean Ct values (A) and positive test counts for SARS CoV-2 S-gene–positive tests (B) for February 1, 2020, through November 30, 2021, according to a gamma model. Break points detected through iterative sequential regression (ISR) that indicate significant changes in mean Ct values and positive tests are labeled. Blue line represents estimated S− mean Ct value and positive test counts by ISR. Blue lines at the base of the graph represent 95% CIs around the breakpoints estimated by the ISR model. Ct, cycle threshold; S, spike; S+, presence of S gene; S−, absence of S gene.

Figure 4. Emergence of novel Delta variant of SARS CoV-2 in England, showing mean Ct values (A) and positive test counts for SARS CoV-2 S-gene–positive tests (B) for February 1, 2020, through November 30, 2021, according to a gamma model. Break points detected through iterative sequential regression (ISR) that indicate significant changes in mean Ct values and positive tests are labeled. Blue line represents estimated S− mean Ct value and positive test counts by ISR. Blue lines at the base of the graph represent 95% CIs around the breakpoints estimated by the ISR model. Ct, cycle threshold; S, spike; S+, presence of S gene; S−, absence of S gene.

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Page created: August 16, 2023
Page updated: September 20, 2023
Page reviewed: September 20, 2023
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