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Published on 14.08.20 in Vol 22, No 8 (2020): August

Preprints (earlier versions) of this paper are available at http://preprints.jmir.org/preprint/20914, first published Jun 04, 2020.

This paper is in the following e-collection/theme issue:

    Original Paper

    The Infection Rate of COVID-19 in Wuhan, China: Combined Analysis of Population Samples

    1Center for Applied Genomics, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States

    2Department of Radiation Oncology, Sun Yat-sen University Cancer Center, Guangzhou, China

    3Institute of Allergy and Immunology, School of Medicine, Shenzhen University, Shenzhen, China

    4Divisions of Human Genetics and Pulmonary Medicine, The Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States

    Corresponding Author:

    Hakon Hakonarson, MD, PhD

    Center for Applied Genomics

    The Children’s Hospital of Philadelphia

    3615 Civic Center Boulevard

    Philadelphia, PA

    United States

    Phone: 1 267 426 0088

    Email: Hakonarson@email.chop.edu


    ABSTRACT

    Background: The coronavirus disease (COVID-19) pandemic began in Wuhan, China, in December 2019. Wuhan had a much higher mortality rate than the rest of China. However, a large number of asymptomatic infections in Wuhan may have never been diagnosed, contributing to an overestimated mortality rate.

    Objective: This study aims to obtain an accurate estimate of infections in Wuhan using internet data.

    Methods: In this study, we performed a combined analysis of the infection rate among evacuated foreign citizens to estimate the infection rate in Wuhan in late January and early February.

    Results: Based on our analysis, the combined infection rate of the foreign evacuees was 0.013 (95% CI 0.008-0.022). Therefore, we estimate the number of infected people in Wuhan to be 143,000 (range 88,000-242,000), which is significantly higher than previous estimates. Our study indicates that a large number of infections in Wuhan were not diagnosed, which has resulted in an overestimated case fatality rate.

    Conclusions: Increased awareness of the original infection rate of Wuhan is critical for proper public health measures at all levels, as well as to eliminate panic caused by overestimated mortality rates that may bias health policy actions by the authorities.

    J Med Internet Res 2020;22(8):e20914

    doi:10.2196/20914

    KEYWORDS



    Introduction

    In December 2019, the first cases of coronavirus disease (COVID-19) were reported in Wuhan, China, a megacity with a population of approximately 11 million people. To prevent the spread of this highly infectious disease, the government initiated a city-wide lockdown on January 23, 2020. However, despite these efforts, COVID-19 spread to many countries across the world, reaching pandemic levels, and continues to be a serious public health concern due to its high mortality rate. According to the large-sample analysis by Wu and McGoogan [1], China’s case fatality rate (CFR) was 2.3%—that is, 1023 deaths from 44,672 confirmed cases as of February 11, 2020, with a significant proportion of cases originating from Wuhan. The large number of infected people in Wuhan put a tight strain on essential medical resources. The city had a much higher mortality rate (according to Feb 10th statistics: CFR=4.05% [748 deaths/18,454 diagnoses]; Apr 24th statistics: CFR=7.69% [3869 deaths/50,333 diagnoses]) than the rest of China. The overall CFR of 2.3% for China was likely overestimated, due to strained medical resources and a large number of undiagnosed patients. According to a recent study, 78% of those who had been infected were asymptomatic [2]. Therefore, a large number of asymptomatic infections in Wuhan might have never been diagnosed, which contributed to the overestimated CFR. An accurate estimation of the infection rate is therefore important to assess Wuhan’s CFR precisely.


    Methods

    Using Markov Chain Monte Carlo methods, Wu et al [3] estimated that 75,815 individuals (95% CI 37,304-130,330) had been infected in Wuhan as of January 25, 2020. Following this, a number of foreign governments evacuated their citizens and performed thorough etiological tests on them. This group of evacuees can serve as a “random” sample to estimate the infection rate in Wuhan. With internet search as an important source of epidemiologic information on COVID-19 [4], we performed a combined analysis of the infection rates of these population samples using publicly available data (Table 1), instead of a simple pooled calculation, considering potential differences in lifestyles and pathogen exposure across different populations. The combined analysis was done using the Comprehensive Meta-Analysis Software (Biostat, Inc).

    Table 1. Number of infected people from different countries.
    View this table

    Results

    Our analysis demonstrates that there is no significant heterogeneity across different population samples (heterogeneity test P=.491). The combined infection rate is 0.013 (95% CI 0.008-0.022) (Figure 1). Based on our results, we estimate the number of infected people in Wuhan, China, to be 143,000 (range 88,000-242,000), which is significantly higher than the estimate proposed by Wu et al [3].

    Figure 1. Combined analysis of infection rates of different populations.
    View this figure

    Discussion

    Our estimate indicates that a large number of infections in Wuhan were not diagnosed. The number of undiagnosed cases in late January and early February is larger than the final diagnosed count reported to date (n=50,333), which has resulted in an overestimated CFR. In addition, our study suggests that the lower CFR (0.51%) estimated by the Centre for Evidence-Based Medicine [15] does not indicate viral variants and loss of virulence. Taken together, increased awareness of the original infection rates in Wuhan, China, is critically important for appropriate public health measures at all levels, as well as to eliminate panic caused by overestimated mortality rates that may bias health policy actions by the authorities.

    Acknowledgments

    The study was supported by Institutional Development Funds from the Children’s Hospital of Philadelphia to the Center for Applied Genomics, The Children’s Hospital of Philadelphia Endowed Chair in Genomic Research to HH.

    Authors' Contributions

    HQ was responsible for the literature search, study design, data collection, data analysis, data interpretation, and writing; ZJC was involved in data collection; ZD in data interpretation; LT in study design and data interpretation; and HH in study design, data interpretation, and writing.

    Conflicts of Interest

    None declared.

    References

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    Abbreviations

    COVID-19: coronavirus disease
    CFR: case fatality rate


    Edited by G Eysenbach; submitted 04.06.20; peer-reviewed by W Zhang, P Banik; comments to author 18.07.20; revised version received 18.07.20; accepted 22.07.20; published 14.08.20

    ©Hui-Qi Qu, Zhangkai Jason Cheng, Zhifeng Duan, Lifeng Tian, Hakon Hakonarson. Originally published in the Journal of Medical Internet Research (http://www.jmir.org), 14.08.2020.

    This is an open-access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work, first published in the Journal of Medical Internet Research, is properly cited. The complete bibliographic information, a link to the original publication on http://www.jmir.org/, as well as this copyright and license information must be included.