Estimating the human bottleneck for contact tracing

Abstract

The SARS-CoV-2 pandemic has highlighted the importance of contact tracing for epidemiological mitigation. Contact tracing interviews (CTIs) typically rely on episodic memory, which is prone to decline over time. Here, we provide a quantitative estimate of reporting decline for age- and gender-representative samples from the United Kingdom and Germany, emulating >15,000 CTIs. We find that the number of reported contacts declines as a power function of recall delay and is significantly higher for younger subjects and for those who used memory aids, such as a scheduler. We further find that these factors interact with delay: Older subjects and those who made no use of memory aids have steeper decline functions. These findings can inform epidemiological modeling and policies in the context of infectious diseases.

Keywords: contact tracing; forgetting; memory; under-reporting.

Fig. 1.

Memory decline for the United Kingdom and GER samples. Scatter points in (A–D) and (G–J) show the average number of reported contacts for 1–14 days of reporting delay. The corresponding line fits show the best fitting power functions. A and G) show the data for all respective subjects, B, C, H, and I) split the data according to age and aid use, indicated by hue and saturation as labeled. D and J) split the data into finer age brackets as indicated by hue, as labeled. Bars in (E, F) and (K, L) show the best fitting slopes of the corresponding power functions. Gray error bars indicate 95% confidence intervals. O, overall; YA, younger subjects using aids; YNA, younger subjects using no aids; OA, older subjects using aids; ONA, older subjects using no aids.