Fig. 4. Impact of SARS-CoV-2 testing rates on the capacity to monitor changes in variant prevalence based on diagnostic test availability and proportion of test-positive samples sequenced.

Different genomic surveillance strategies (that is, all specimens collected from all healthcare facilities sent to one facility to be sampled for sequencing (population-wide strategy); or only one tertiary facility or 10, 25, 50 or 100% of tertiary sentinel facilities would sample the specimens they collected for sequencing) were simulated. a, Maximum absolute difference between observed and circulating variant proportions. b, Proportion of time points when sequencing was performed that the absolute difference between observed and circulating variant proportions is greater than 20%. All results were computed from 1,000 random independent simulations for each surveillance strategy.