The effectiveness of quarantine and isolation determine the trend of the COVID-19 epidemic in the final phase of the current outbreak in China

Abstract

Objectives: Since January 23, 2020, stringent measures for controlling the novel coronavirus epidemic have been gradually enforced and strengthened in mainland China. The detection and diagnosis have been improved, as well. However, the daily reported cases remaining at a high level make the epidemic trend prediction difficult.

Methods: Since the traditional SEIR model does not evaluate the effectiveness of control strategies, a novel model in line with the current epidemic's process and control measures was proposed, utilizing multisource datasets including the cumulative number of reported, deceased, quarantined and suspected cases.

Results: Results show that the trend of the epidemic mainly depends on quarantined and suspected cases. The predicted cumulative numbers of quarantined and suspected cases nearly reached static states, and their inflection points have already been achieved, with the epidemic's peak coming soon. The estimated effective reproduction numbers using model-free and model-based methods are decreasing, as well as new infections, while newly reported cases are increasing. Most infected cases have been quarantined or put in the suspected class, which has been ignored in existing models.

Conclusions: The uncertainty analyses reveal that the epidemic is still uncertain, and it is important to continue enhancing the quarantine and isolation strategy and improving the detection rate in mainland China.

Keywords: Coronavirus; Mathematical model; Multisource data; SEIR model.

Figure 1

The datasets related to the COVID-19 epidemic, including newly reported cases, cumulative number of reported cases, cumulative number of cured cases, cumulative number of death cases, cumulative quarantined cases, and cumulative suspected cases.

Figure 2

Diagram of the model adopted in the study for simulating the COVID-19 infection. Interventions, including intensive contact tracing, followed by quarantine and isolation, are indicated. The gray compartment means a suspected case compartment consisting of contact tracing Eq and fever clinics.

Figure 3

(A) Cumulative number of confirmed reported cases for mainland China, Hubei province and Wuhan city, (B) Estimated number of illness onset cases for mainland China, Hubei province and Wuhan city, (C) Estimated basic reproduction number R₀.

Figure 4

Estimated effective reproduction number R_t for mainland China in (A) and for Hubei province in (B). The timing of strategies implemented are as follows: (C1) Huanan Seafood Wholesale Market closed on January 1, 2020; (C2) Detection kits for COVID-19 first used on January 16, 2020; (C3) The Chinese government amended the Law on the Prevention and Treatment of Infectious Diseases to include COVID-19 as a class-B infection but manage it as a class-A infection due to its severity on January 20, 2020; (C4) Lock-down strategy in Wuhan implemented on January 23, 2020; (C5) Spring festival holiday extended and self-quarantine measures kept on January 26, 2020.

Figure 5

Best model fitting results (black curves) and variation in cumulative number of reported cases, cumulative number of death cases, cumulative quarantined cases, and cumulative suspected cases with the minimum contact rate (c_b), detection rate (b), and the confirmation ratio (f).

Figure 6

Best model fitting results (black curves) and variation in cumulative number of reported cases, cumulative number of death cases, and cumulative quarantined cases with the minimum contact rate (c_b), detection rate (b), and the confirmation ratio (f) for Hubei Province.

Figure 7

The impact of the randomness of the cumulative reporting data sets, including cumulative number of reported cases, cumulative number of death cases, cumulative quarantined cases and cumulative suspected cases on the 2019nCov epidemic in mainland China. The unilateral 95% confidence intervals (here 95% upper confidence limits) have been given, and the mean curve and estimated curve based on the real data sets are marked in each subplot.

Figure 8

The hospital notifications, effective reproduction numbers, and estimated contact rate, quarantined rate and diagnose rate curves for mainland China (A–C) and the Hubei province (D–F).