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Phylogenetic trees. Phylogenetic analysis of 4 school SARS-CoV-2 outbreaks (A–D). Staff cases are indicated in all upper-case letters, while student cases are in lowercase letters. Individuals that were symptomatic at the time of collection have open circles, and cases asymptomatic at the time of collection have closed circles. All trees are rooted to the reference genome MN908947.3 with the scale representing nucleotide substitutions per site based on the full viral genome.
