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Changes in (a) daily COVID-19 cases in Tijuana, Mexico and (b) case:flow ratio (filled gray circles) plotted alongside SARS-CoV-2 RNA concentrations measured using the N1 marker (filled black squares) and LOD (filled black triangles) in the Tijuana River from July 2020 to May 2021. b uses log scale for both the accumulating case:flow rate ratio and SARS-CoV-2 RNA concentrations.
