How Efficient is Contact Tracing in Mitigating the Spread of Covid-19? A Mathematical Modeling Approach

The paper derives, from a detailed compartmental CT model, (i) an upper bound Rc < κ(1−s)/s under perfect tracking and monitoring, and (ii) Rc = κ(1−s)/s + κM when tracking is perfect and either monitoring or reporting is perfect; it also proves the convex-combination forms Rc = (1−ε)R0 + εRM and Rc = (1−ε)R0 + εRT with the thresholds ε > (1−1/R0)/(1−θ1) and ε > (1−1/R0)/(1−θ2), respectively. These appear explicitly in the manuscript (e.g., κ, s defined in eqs. (4)–(5); Rc < κ(1−s)/s; and the two special-case convex combinations and thresholds) . The candidate solution reaches the same formulas via a heuristic traced/untraced decomposition—using κ = s·RU and convex combinations—rather than the paper’s next-generation-matrix route. Minor issues: the candidate briefly suggests s = ε in a “perfect monitoring” context (true only under perfect reporting), and the paper contains notational inconsistencies for R0 in special cases; but the core results coincide and are correct as stated in both accounts .