Fig. 4

Incremental efficiency plots for selected surveillance strategies relative to a reference strategy of only testing individuals with severe COVID-like symptoms. Here, improvement in COVID-19 surveillance (x-axis) is balanced against additional nasopharyngeal swabs used (y-axis for a) and additional RT-PCR tests conducted (y-axis for b) until outbreaks were detected. Both axes are log₁₀-adjusted. For both panels, daily testing capacity is fixed at 1 test/day (for higher testing capacities, see Additional File 2: Fig. S7). Small translucent points represent median outcomes across 100 surveillance simulations for each simulated outbreak, and larger opaque points represent mean of medians across all outbreaks