Fig 1.
Static-temporal multiplex network model and social contact pattern.
A A schematic illustration of the static-temporal multiplex network, which is composed of two layers: static contact layer and temporal contact layer. The links on the static contact layer represent regular interactions occurring in households, schools, and workplaces, whereas those on the temporal contact layer represent occasional contacts occur in gatherings and events. The links on the static contact layer are constant, whereas the links on the temporal layer are updated every day. B The age-specific contact frequency from the survey and the synthesized static layer. C The age-specific proportion of individuals joining gathering and events. D The size distribution of gathering and events.
Fig 2.
Example of the Test-Trace-Isolate strategy.
Once the primary case A develops symptoms, the sample is collected with delay. After the sample collection, A’s contacts on the temporal contact layer are disconnected until the test result is returned. If the test result is positive (which is the case in this figure), A is isolated, thus the contacts on both layers are disconnected over 14 days. If the test result is negative (i.e., false negative), the disconnected links recover. A infects individual B through a contact on the temporal contact layer (before A’s sample collection) and infects individual C through a contact on the static contact layer before the test result is returned. Individuals B and C are traced and tested immediately after the infection of A is confirmed. The links of B and C on the temporal layer are disconnected until the test results are returned. If the infection of the traced individuals (B in this figure) is confirmed, further contact trace is triggered. If the infection of the traced individuals (C in this figure) is not confirmed (i.e., false negative), the disconnected links recover.
Fig 3.
Effectiveness and social/implementation cost of TTI.
A Infection attack rate (IAR) without TTI strategy (unmitigated) and reduction in the cumulative infections by the Test-Trace-Isolate strategy (baseline) with different reproduction number R0. The vertical error bars indicate the 95% CI. B as in A, but for the number of deaths per 1,000 people and reduction in deaths. C Peak daily number of traced individuals with positive test results (thus contact tracing is needed) per 1,000 people. D Peak daily number of simultaneously isolated individuals per 1,000 people.
Fig 4.
Sensitivity analyses varying the parameters regulating the test and trace processes.
A Reductions in the cumulative infections with different probabilities that contacts on the temporal layer to be successfully traced. The vertical error bars indicate the 95% CI. B as in A, but the days to trace contacts on the temporal contact layer before sample collection of the primary cases were varied. C as in A, but the time from symptom onset to sample collection was varied. D as in A, but the time from sample collection to laboratory diagnosis was varied.
Fig 5.
Analysis of baseline with longer delay varying the time from sample collection to laboratory diagnosis.
A Reduction in the cumulative infections. B True positive rate among the traced individuals. “Tcr = 1 (baseline)” and “Tcr = 4” are the models setting the time from sample collection to laboratory diagnosis as 1 day or 4 days, respectively. “Tcr = 1 (null model)” is the model setting the time from sample collection to laboratory diagnosis as 1 day, but the true positive rate among the traced individuals is the same as the model with “Tcr = 4”. Other parameter settings are the same.
Fig 6.
Effectiveness and burden of TTI-relaxed and TTI-strict.
A Reductions in the cumulative infections with different TTI strategies. (TTI-relaxed) Contacts on both layers remains while the test results are waited. (TTI-strict) Contacts on both layers are disconnected while the test results are waited. B as in A, but for the mean isolation period.
Fig 7.
Effectiveness of reactive distancing policy coupled with the TTI strategy.
A and B Reactive social distancing: a fraction of contacts on temporal contact layer are disconnected. A for the reduction in the cumulative infections, B as in A, but for the reduction in deaths. C and D Reactive all-level distancing: 50% of contacts on temporal layer are disconnected and a fraction of contacts on static contact layer is disconnected. C for the reduction in the cumulative infections, D as in C, but for the reduction in deaths. Those policies are triggered when the cumulative number of detected cases exceeds 50.