The epidemiological characteristics and effectiveness of countermeasures to contain coronavirus disease 2019 in Ningbo City, Zhejiang Province, China

Xuying Lao,Yi Chen,Yao Wang,Rong Wang,Keqin Ding,Li Luo,Dongliang Zhang,Bo Yi,Yuhui Liu,Meng Yang,Tianmu Chen,Yuanzhao Zhu,Ting Fang,Jingwen Xu,Zeyu Zhao,Jia Rui,Zhao Lei

doi:10.1038/s41598-021-88473-4

Xuying Lao, Yi Chen + Show 15 more

Open Access

https://doi.org/10.1038/s41598-021-88473-4

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Abstract

A novel coronavirus (SARS-CoV-2) has spread worldwide and led to high disease burden around the world. This study aimed to explore the key parameters of SARS-CoV-2 infection and to assess the effectiveness of interventions to control the coronavirus disease 2019 (COVID-19). A susceptible—exposed—infectious—asymptomatic—recovered (SEIAR) model was developed for the assessment. The information of each confirmed case and asymptomatic infection was collected from Ningbo Center for Disease Control and Prevention (CDC) to calculate the key parameters of the model in Ningbo City, China. A total of 157 confirmed COVID-19 cases (including 51 imported cases and 106 secondary cases) and 30 asymptomatic infections were reported in Ningbo City. The proportion of asymptomatic infections had an increasing trend. The proportion of elder people in the asymptomatic infections was lower than younger people, and the difference was statistically significant (Fisher’s Exact Test, P = 0.034). There were 22 clusters associated with 167 SARS-CoV-2 infections, among which 29 cases were asymptomatic infections, accounting for 17.37%. We found that the secondary attack rate (SAR) of asymptomatic infections was almost the same as that of symptomatic cases, and no statistical significance was observed (χ2 = 0.052, P = 0.819) by Kruskal–Wallis test. The effective reproduction number (Reff) was 1.43, which revealed that the transmissibility of SARS-CoV-2 was moderate. If the interventions had not been strengthened, the duration of the outbreak would have lasted about 16 months with a simulated attack rate of 44.15%. The total attack rate (TAR) and duration of the outbreak would increase along with the increasing delay of intervention. SARS-CoV-2 had moderate transmissibility in Ningbo City, China. The proportion of asymptomatic infections had an increase trend. Asymptomatic infections had the same transmissibility as symptomatic infections. The integrated interventions were implemented at different stages during the outbreak, which turned out to be exceedingly effective in China.

Highlights

The coronavirus disease 2019 (COVID-19), with the pathogen of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread worldwide and led to significant disease burden around the world, especially in China, South Korea, Japan, Iran, and the United States of America[1,2,3,4,5]
We employed the SEIAR model to fit the data of SARS-CoV-2 symptomatic and asymptomatic infections in the city, and aimed to calculate the key parameters, and further to assess the effectiveness of interventions implemented in Ningbo City, Zhejiang Province, China
As of February 25, 2020, a total of 157 confirmed COVID-19 cases and 30 asymptomatic infections were reported in Ningbo City

Summary

Introduction

The coronavirus disease 2019 (COVID-19), with the pathogen of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread worldwide and led to significant disease burden around the world, especially in China, South Korea, Japan, Iran, and the United States of America[1,2,3,4,5]. Rapid increase in the number of confirmed cases, wide range of countries affected, and enormous impact on people’s health and national economies prioritized the importance of understanding the epidemiological characteristics and the transmission mechanism of COVID-19. As the most affected country in the first wave of epidemic transmission, it is essential to assess the effectiveness of interventions implemented in China during the outbreak and to share out the experience of disease control for other countries to prepare for the possible following wave(s) of the outbreak. We employed the SEIAR model to fit the data of SARS-CoV-2 symptomatic and asymptomatic infections in the city, and aimed to calculate the key parameters (including the proportion and the transmissibility of the asymptomatic infections), and further to assess the effectiveness of interventions implemented in Ningbo City, Zhejiang Province, China

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