1. Early detection of variants of concern via funnel plots of regional reproduction numbers.
- Author
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Milanesi, Simone, Rosset, Francesca, Colaneri, Marta, Giordano, Giulia, Pesenti, Kenneth, Blanchini, Franco, Bolzern, Paolo, Colaneri, Patrizio, Sacchi, Paolo, De Nicolao, Giuseppe, and Bruno, Raffaele
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STATISTICAL process control , *REPRODUCTION , *SARS-CoV-2 , *FALSE alarms , *SCATTER diagrams , *HOSPITAL statistics - Abstract
Early detection of the emergence of a new variant of concern (VoC) is essential to develop strategies that contain epidemic outbreaks. For example, knowing in which region a VoC starts spreading enables prompt actions to circumscribe the geographical area where the new variant can spread, by containing it locally. This paper presents 'funnel plots' as a statistical process control method that, unlike tools whose purpose is to identify rises of the reproduction number ( R t ), detects when a regional R t departs from the national average and thus represents an anomaly. The name of the method refers to the funnel-like shape of the scatter plot that the data take on. Control limits with prescribed false alarm rate are derived from the observation that regional R t 's are normally distributed with variance inversely proportional to the number of infectious cases. The method is validated on public COVID-19 data demonstrating its efficacy in the early detection of SARS-CoV-2 variants in India, South Africa, England, and Italy, as well as of a malfunctioning episode of the diagnostic infrastructure in England, during which the Immensa lab in Wolverhampton gave 43,000 incorrect negative tests relative to South West and West Midlands territories. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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