Assessing the effectiveness of test-trace-isolate interventions using a multi-layered temporal network

TL;DR

This study models the effectiveness of test-trace-isolate strategies for infectious disease control using a multi-layered temporal network, highlighting their limitations and benefits depending on the reproduction number.

Contribution

It introduces a novel multi-layer temporal contact network model to evaluate TTI strategies' impact on outbreak containment and mitigation, specifically for SARS-CoV-2.

Findings

TTI can contain outbreaks up to R0 of 1.3 with 88.2% prevention potential.

Higher R0 values reduce TTI effectiveness, requiring longer quarantines.

Combining TTI with social distancing improves containment chances but remains limited at high R0.

Abstract

In the early stage of an infectious disease outbreak, public health strategies tend to gravitate towards non-pharmaceutical interventions (NPIs) given the time required to develop targeted treatments and vaccines. One of the most common NPIs is Test-Trace-Isolate (TTI). One of the factors determining the effectiveness of TTI is the ability to identify contacts of infected individuals. In this study, we propose a multi-layer temporal contact network to model transmission dynamics and assess the impact of different TTI implementations, using SARS-CoV-2 as a case study. The model was used to evaluate TTI effectiveness both in containing an outbreak and mitigating the impact of an epidemic. We estimated that a TTI strategy based on home isolation and testing of both primary and secondary contacts can contain outbreaks only when the reproduction number is up to 1.3, at which the epidemic prevention potential is 88.2% (95% CI: 87.9%-88.5%). On the other hand, for higher value of the reproduction number, TTI is estimated to noticeably mitigate disease burden but at high social costs (e.g., over a month in isolation/quarantine per person for reproduction numbers of 1.7 or higher). We estimated that strategies considering quarantine of contacts have a larger epidemic prevention potential than strategies that either avoid tracing contacts or require contacts to be tested before isolation. Combining TTI with other social distancing measures can improve the likelihood of successfully containing an outbreak but the estimated epidemic prevention potential remains lower than 50% for reproduction numbers higher than 2.1.