Phase 5 started from January 27, 2020 to the end of the study period, corresponding to the sustained massive national efforts, plus frequent emphases. Different from the previous four phases, reductions in the estimated Pi during this phase were not an indication of under-detection but an indication of declines in the epidemic reflected by the detected and confirmed cases of COVID-19. This is because the model predicted Pi did not consider any interventions but natural growth of the epidemic.