Summary
Objective
The ongoing novel coronavirus disease 2019 (COVID-19) is the leading cause of morbidity and mortality due to its contagious nature and absence of vaccine and treatment. Although numerous primary studies reported extremely variable case fatality rate (CFR) of COVID-19, no review study attempted to estimate the CFR of COVID-19. The current systematic review and meta-analysis were aimed to assess the pooled CFR of COVID-19.
Methods
Electronic databases: PubMed, Science Direct, Scopus, and Google Scholar were searched to retrieve the eligible primary studies that reported CFR of COVID-19. Keywords: (“COVID-19”OR “COVID-2019” OR “severe acute respiratory syndrome coronavirus 2”OR “severe acute respiratory syndrome coronavirus 2” OR “2019-nCoV” OR “SARS-CoV-2” OR “2019nCoV” OR ((“Wuhan” AND (“coronavirus” OR “coronavirus”)) AND (2019/12[PDAT] OR 2020[PDAT]))) AND (“mortality “OR “mortality” OR (“case” AND “fatality” AND “rate”) OR “case fatality rate”) were used as free text and MeSH term in searching process. A random-effects model was used to estimate the CFR in this study. I2 statistics, Cochran’s Q test, and T2 were used to assess the functional heterogeneity between included studies.
Results
The overall pooled CFR of COVID 19 was 10.0%(95% CI: 8.0-11.0); P < 0.001; I2 = 99.7). The pooled CFR of COVID-19 in general population was 1.0% (95% CI: 1.0-3.0); P < 0.001; I2 = 94.3), while in hospitalized patients was 13.0% (95% CI: 9.0-17.0); P < 0.001, I2 = 95.6). The pooled CFR in patients admitted in intensive care unit (ICU) was 37.0% (95% CI: 24.0-51.0); P < 0.001, I2 = 97.8) and in patients older than 50 years was 19.0% (95% CI: 13.0-24.0); P < 0.001; I2 = 99.8).
Conclusion
The present review results highlighted the need for transparency in testing and reporting policies and denominators used in CFR estimation. It is also necessary to report the case’s age, sex, and the comorbidity distribution of all patients, which essential in comparing the CFR among different segments of the population.
Keywords: Case fatality rate, COVID-19, Meta-analysis, Epidemic, Epidemiology
Introduction
The ongoing coronavirus 2019 (COVID-19) was initially reported from Wuhan, China, in December 2019. After few weeks, it has been involved in several countries and became a significant global public health problem [1-3]. World Health Organization (WHO) designated COVID-19 as a pandemic disease on March 11, 2020 (WHO, situational Report-52). The most known symptoms of COVID-19 are fever, cough, shortness of breathing, and occasional watery diarrhea [4]. Even though COVID-19 often causes mild symptoms compared to other respiratory infections, it can cause severe illness in certain groups of people, such as the elderly and people with major underlying health problems (cardiovascular disease and diabetes) [5].
There are two key parameters to understand the epidemiological features of an outbreak or epidemic. These are primary reproduction numbers (R0) and case-fatality rates (CFR) [6, 7]. The R0 is an epidemiologic metric that has been used to assess the infectiveness of the agents that cause an outbreak. This index explains the average number of new cases generated from an infected person. The higher amount of R0 indicates the highest transmissibility of the infection agent. An estimated R0 of the COVID-19 virus is 3.32, which means one infected case can transmit the virus to 3 to 4 susceptible individuals [8]. CFR is another essential index that helps to understand the epidemiological characteristics of an outbreak. The CFR of COVID-19 is defined as the number of deaths in COVID-19 cases divided by the total number of people infected by COVID-19 [9]. Previously reported CFR of COVID-19 is highly variable. The primary cause of this heterogeneity could be varied as a result of surveillance systems sensitivity. Surveillance system sensitivity low due to more than 80% of cases does not show symptoms of the disease or show mild symptoms. Thus, cases missed by the surveillance system are not considered in the denominator and could lead to overestimation of CFR [10, 11]. Several primary studies have been conducted to estimate the CFR of COVID-19 across the world and reported extremely heterogeneous magnitude. However, no review study has attempted to estimate pooled CRF of COVID-19 from the available literature to understand better the nature of an outbreak and the virulence of the disease. Thus, the current study was aimed to estimate pooled CFR of COVID-19 from primary studies reported from different countries using systematic review and meta-analysis.
Materials and methods
SEARCH STRATEGY
This systematic review and meta-analysis were performed to estimate pooled CRF of COVID-19 from the primary studies published in international electronic databases. Electronic databases: PubMed, Scopus, Science Direct, and Google Scholar were searched to retrieve eligible studies that were conducted to estimate CFR of COVID-19. Keywords: (“COVID-19”OR “COVID-2019” OR “severe acute respiratory syndrome coronavirus 2”OR “severe acute respiratory syndrome coronavirus 2” OR “2019-nCoV” OR “SARS-CoV-2” OR “2019nCoV” OR ((“Wuhan” AND (“coronavirus” OR “coronavirus”)) AND (2019/12[PDAT] OR 2020[PDAT]))) AND (“mortality “OR “mortality” OR (“case” AND “fatality” AND “rate”) OR “case fatality rate”) were used in free text and MeSH terms.
STUDY SELECTION AND DATA EXTRACTION
All studies published in 2020 and reported CFR for COVID-19 were included in this review (Fig. 1). From each included study, extracted information on the first author’s name, the country from where the study was reported, year of study, sample size, type of study, age, gender, comorbidity, and CFR with a 95% confidence interval (Tab. I and II).
Fig. 1.
PRISMA Flow Diagram for included studies in the current meta-analysis.
Tab. I.
Included studies in the current meta-analysis.
The first author (publication year) | Country | Sample size | Sex of participant | Mean/med of age | Study design (randomization, blinding) | Study based | CFR estimation |
---|---|---|---|---|---|---|---|
Wang et al. (2020) [13] | China | 138 | Both | 58 | Retrospective single-center case series | Hospitalized | 0.043 |
Grasselli et al. (2020) [14] | Italy | 1591 | Both | 63 | Retrospective, case series | ICU, Hospitalized, Total | 0.26 |
Grasselli et al. (2020) [14] | Italy | 786 | Both | 64<= | Retrospective, case series | ICU, Hospitalized | 0.36 |
Grasselli et al. (2020) [14] | Italy | 795 | Both | <=63 | Retrospective, case series | ICU, Hospitalized | 0.15 |
Guo et al. (2020)[15] | China | 187 | Both | 58.5 | Retrospective, single-center case series | Hospitalized | 0.23 |
Wei et al. (2020) [16] | China | 1975 | Both | Cross-sectional | Unknown | 0.0284 | |
Yin et al. (2020) [17] | China | 449 | Both | 65.1 | Retrospective-cohort | Hospitalized | 0.298 |
Chen et al. (2020) [18] | China | 99 | Both | 55.5 | Retrospective, single-center study | Hospitalized | 0.11 |
Xiaobo Yang et al. (2020)[19] | China | 52 | Both | 59.7 | Retrospective observational | ICU, Hospitalized | 0.615 |
Zhou et al. (2020) [20] | china | 191 | Both | 56 | Retrospective cohort | Hospitalized | 0.2827 |
Barrasa et al. (2020) [21] | Spain | 48 | Both | 63 | Cross-sectional | ICU, Hospitalized | 0.13 |
Tang et al. (2020) [22] | China | 179 | 67 | Retrospective case-control | Hospitalized | 0.288 | |
Lei et al (2020) [23] | China | 34 | Both | 55 | Retrospective review patient | Hospitalized, Total | 0.206 |
Lei et al (2020) [23] | China | 15 | Both | 55 | Retrospective review patient | ICU admitted | 0.467 |
Lei et al (2020) [23] | China | 19 | Both | 47 | Retrospective review patient | Hospitalized | 0 |
Shim et al. (2020) [5] | South-Korea | 6284 | Both | NR | Cross-sectional | General Population, Total | 0.007 |
Shim et al. (2020) [5] | South-Korea | 2345 | Male | NR | Cross-sectional | General Population | 0.011 |
Shim et al. (2020) [5] | South-Korea | 3939 | Female | NR | Cross-sectional | General Population | 0.004 |
Li et al (2020) [24] | China | 279 | Both | 56 | Ambispective cohort study | Hospitalized | 0.011 |
Li et al (2020) [24] | China | 269 | Both | 65 | Ambispective cohort study | ICU admitted | 0.325 |
Tian et al. (2020) [25] | China | 262 | Both | 47.5 | Retrospective | Hospitalized | 0.009 |
Tian et al. (2020) [25] | China | 46 | Both | 61.4 | Retrospective | Hospitalized | 0.065 |
Tian et al. (2020) [25] | China | 216 | Both | 44.5 | Retrospective | General Population | 0 |
Liu et al. (2020) [26] | China | 56 | Both | NR | Retrospective study | Hospitalized, Total | NR |
Liu et al. (2020)[26] | China | 18 | Both | 68 | Retrospective study | Hospitalized | 0.0556 |
Liu et al. (2020)[26] | China | 38 | Both | 47 | Retrospective study | Hospitalized | 0.0526 |
Liu et al. (2020) [27] | China | 245 | Both | 43.95 | Retrospective cohort | Hospitalized | 0.1347 |
Lei et al (2020) [28] | China | 20 | Both | 43.2 | Cross-sectional | Hospitalized | 0 |
Sun et al. (2020) [29] | China | 288 | Both | 44 | Cross-sectional | Unknown | 0.135 |
Mei et al (2020) [30] | World | 96580 | Both | Cross-sectional | Unknown | 0.0363 | |
Cao et al. et al. (2020) [31] | China | 199 | Both | 58 | Randomized, controlled, open-label trial | Hospitalized | 0.161 |
Cao et al. (2020) [31] | China | 99 | Both | 58 | Randomized, controlled, open-label trial | Hospitalized | 0.152 |
Cao et al. (2020) [31] | China | 100 | Both | 58 | Randomized, controlled, open-label trial | Hospitalized | 0.17 |
Bhatraju et al. (2020) [32] | USA | 24 | Both | 64 | Retrospective case series | Hospitalized | 0.5 |
Grein et al. (2020) [33] | USA, Canada, Europe, Japan | 53 | Both | 64 | Cohort | Hospitalized | 0.13 |
Grein et al. (2020) [33] | USA, Canada, Europe, Japan | 34 | Both | 67 | Cohort | Hospitalized | 0.18 |
Grein et al. (2020) [33] | USA, Canada, Europe, Japan | 19 | Both | 53 | Cohort | Hospitalized | 0.05 |
Liang et al. (2020) [34] | China | 1590 | Both | 48.9 | Retrospective cohort | General Population | 0.031 |
Liang et al. (2020) [34] | China | 647 | Both | 55.1 | Retrospective cohort | General Population | 0.073 |
Liang et al. (2020) [34] | China | 943 | Both | 44.6 | Retrospective cohort | General Population | 0.003 |
Gao et al. (2020) [35] | China | 54 | Both | 60.4 | Cohort | Hospitalized | 0.333 |
Du et al. (2020) [36] | China | 109 | Both | 70.7 | Multi-center observational | ICU | 0.661 |
Du et al. (2020)[36] | China | 51 | Both | 68.4 | Multi-center observational | ICU | 0.706 |
Du et al. (2020) [36] | China | 58 | Both | 72.7 | Multi-center observational | Hospitalized | 0.620 |
Xiao-Wei Xu et al. (2020) [37] | China | 62 | Both | 41 | Retrospective study | Hospitalized | 0 |
Cai et al (2020)[38] | Hong-Kong | 298 | Both | 47.5 | Retrospective study | General Population, Total | 0.01 |
Cai et al (2020)[38] | Hong-Kong | 240 | Both | 41 | Retrospective study | General Population | 0 |
Cai et al (2020)[38] | Hong-Kong | 58 | Both | 62.5 | Retrospective study | General Population | 0.052 |
Cao et al. (2020) [39] | China | 102 | Both | 54 | Cohort | Hospitalized | 0.167 |
Liu et al. (2020)[40] | China | 137 | Both | 57 | Retrospective | Hospitalized | 0.118 |
Young et al. (2020) [41] | Singapore | 18 | Both | 47 | Case-series | Hospitalized, Total | 0 |
Young et al. (2020) [41] | Singapore | 12 | Both | 37 | Case-series | Hospitalized | 0 |
Young et al. (2020) [41] | Singapore | 6 | Both | 56 | Case-series | Hospitalized | 0 |
Wang et al. (2020) [42] | China | 69 | Both | 42 | Retrospective review patient | Hospitalized | 0.075 |
Jian Wu et al. (2020) [2] | China | 80 | Both | 46.1 | Retrospective | Hospitalized | 0 |
McMichael et al. (2020) [43] | USA | 167 | Both | 72 | Cross-sectional | General Population | 0.21 |
Yanli Liu et al. (2020) [44] | China | 383 | Both | 46 | Retrospective cohort | Hospitalized | 0.128 |
Yanli Liu et al. (2020) [44] | China | 68 | Both | 52 | Retrospective cohort | Hospitalized | 0.309 |
Yanli Liu et al. (2020) [44] | China | 315 | Both | 43 | Retrospective cohort | Hospitalized | 0.089 |
Chen et al. (2020) [45] | China | 203 | Both | 54 | Retrospective case series | Hospitalized | 0.128 |
Ning Tang et al. (2020) [46] | China | 183 | Both | 54.1 | Cross-sectional | Hospitalized | 0.115 |
Morteza Abdullatif Khafaie et al. 2020 [47] | World | 337570 | Both | Retrospective-cohort | Unknown | 0.0434 | |
Huang et al. (2020) [48] | China | 41 | Both | 49 | Prospective | Total | 0.15 |
Huang et al. (2020) [48] | China | 13 | Both | 49 | Prospective | ICU | 0.38 |
Huang et al. (2020) [48] | China | 28 | Both | 49 | Prospective cohort | Hospitalized | 0.04 |
Wei-Jie Guan et al. (2020) [49] | China | 926 | Both | 45 | Retrospective | General Population | 0.001 |
Wei-Jie Guan et al. (2020) [49] | China | 173 | Both | 52 | Retrospective | General Population | 0.081 |
Nikpouraghdam et al. (2020) [1] | Iran | 2964 | Both | 55.5 | Retrospective | Hospitalized | 0.086 |
Nikpouraghdam et al. (2020) [1] | Iran | 2964 | Both | 55.5 | Retrospective | General Population | 0.018 |
Tab. II.
The estimated case fatality rate of COVID-19 in different subgroups.
Group | Pooled estimation (%) | 95% CI | Q | I2 (%) |
---|---|---|---|---|
General population | 1.00 | 1.0-3.0 | P < 0.001 | 94.3 |
Hospitalized patients | 13.0 | 9.0-17.0 | P < 0.001 | 95.6 |
ICU admitted | 37.0 | 24.0-51.0 | P < 0.001 | 97.8 |
Unknown | 4.0 | 3.0-5.0 | P < 0.001 | 97.8 |
≤ 50 | 3.0 | 0.0-6.0 | P < 0.001 | 93.7 |
> 50 | 19.0 | 13.0-24.0 | P < 0.001 | 98.1 |
Unknown | 2.0 | 1.0-3.0 | P < 0.001 | 99.8 |
Overall | 10.0 | 8.0-11.0 | P < 0.001 | 99.7 |
STATISTICAL ANALYSIS
Cochran’s Q test’s heterogeneity in the CFR of COVID-19 between different studies was assessed with a significance level of P < 0.1 and I2 statistic with values > 75% [12]. A random-effects meta-analysis model was used to estimate pooled CFR because of the presence of high heterogeneity (I2 = 99.7% and Cochran’s Q (p < 0.001). The univariate meta-regression model was used to assess the effect of sample size on the heterogeneity of pooled CFR. Publication bias was evaluated by Beggs and Eggers tests. Also, the risk of bias analysis performed using the Newcastle-Ottawa Scale for observational studies [13]. Data were analyzed by STATA v 11 (StataCorp, College Station, TX, USA).
Results
Figure 1 depicts the study selection procedure. A total of 516 records were retrieved through electronic databases search, and 324 identified articles after removing 192 pieces due to duplication and irrelevance for the review purpose. The second stape 236 articles were excluded after the title and abstract screeded for the inclusion and exclusion criteria. Of the remaining 88 articles, 49 articles were excluded due to a lack of relevant information or not original articles. Finally, 39 articles reported CFR of COVID-19 were included in the final analysis (Fig. 1 and Table 1).
The Median and IQR (Interquartile range) of reported CFR rate were 8.7%(23.0-1.0). The Minimum and Maximum reported CFR were 0 and 70.6% respectivly (Fig. 2). The overall pooled estimated CFR of COVID-19 was 10.0% (95% CI: 8.0-11.0; P < 0.001, I2 = 99.7) (Fig. 2). The pooled estimated CFR of COVID-19 among general population was 1.0% (95% CI: 1.0-3.0; P < 0.001, I2 = 94.3), while in hospitalised patients 13.0% (95% CI: 9.0-17.0; P < 0.001, I2 = 95.6) (Fig. 2). The pooled estimated CFR of COVID-19 in the patients admited to ICU was 37.0% (95% CI: 24.0-51.0; P < 0.001, I2 = 97.8), and in patients younger than 50 years 3.0% (95% CI: 0.0-6.0; P < 0.001, I2 = 99.2), while the CFR was 19.0% (95% CI: 13.0-24.0; P < 0.001, I2 = 99.8) in patients older than 50 years (Fig. 2 and Table 2). Based on Beggs test there was no publication bias(P = 0.2), but the Eggers tests was shown the presence of publication bias (P < 0.001). Moreover, based on metaregresion regression analysis, ample size was not significantly associated with heatrogeneity of pooled estimated CFR (P = 0.31) (Fig. 3).
Fig. 2.
The forest plot of estimated case fatality rate of COVID-19 in different subgroups.
Fig. 3.
The beggs funnel plot to assess publication bias.
Discussion
The present study systematically reviewed the available literature to estimate the overall pooled CFR COVID-19 and specific subpopulations in patients admitted in hospital, ICU, and old. Based on 39 studies that fulfilled this study, the overall estimated pooled CFR of COVID-19 was 10.0%. The pooled CRF was only 1.0% in the general population, while 29% in patients admitted in ICU and 15% in hospitalized patients.
Although there is limited information on COVID-19 CFR, some primary studies have been reported CFR in different countries with various target populations. For example, the studies reported from Italy have indicated a 9.26% CFR of COVID-19 [47, 50]. Moreover, studies reported from Spain and France have reported 6.16 and 4.21% CFR, respectively [47, 50]. Furthermore, a study reported from Iran shown that 7.9% of CFR, while the study reported from Turkey indicated 2.0% CFR of COVD-19 [47, 50]. Compared to the previous studies cited above, our meta-analysis finding, based on primary studies reported from different countries, indicated CFR with a wide range. This difference between our CFR with its broad range and the previous study could be due to the target population difference.
Moreover, it might be due to case/death finding and reporting capacity between the countries where the primary studies were reported. Furthermore, case and death reporting in some countries might be influenced by political decisions. Thus, these probable reasons could affect the overall estimation of CFR, which could impact the actual epidemiological feature of the disease.
CFR of COVID-19 ranges between 4 and 11% among hospitalized adult patients in different countries based on previous studies [51]. The present study showed that high (13%) CFR in hospital admitted patients. The present study was also revealed that CFR in patients admitted to ICU was 37%. In contrast to our findings, a case series study reported from Seattle indicated high CFR (50%) among critically ill patients [32]. Moreover, a study reported from Washington state the highest CFR (67%) in patients admitted to ICU. Thus the health background of patients admitted to ICU could be an essential factor related to death [52]. For example, among patients admitted to ICU in Washington, 86% have comorbidities such as chronic kidney disease and congestive heart failure [52]. High CFR among patients admitted to ICU is mainly attributable to comorbidities and old age, which exacerbate the morbidity that leads to poor outcomes in patients admitted to ICU. Patients with comorbidities and old age demand great attention to recover from COVID-19, and more evidence requires better understanding to inform health care [32].
The present meta-analysis revealed a significant difference in CFR in the age group younger than 50 years and older (3.0 vs 19%). In Italy, CFR was 52.3 in patients more aged than 80 years and 35.6 in 70-79 years old [9]. Similarly, in Chinese, CFR was high among the most aging patients [53]. Besides CFR differences in age groups, the overall CFR reported from Italy (7.2%) is substantially higher than in China (2.3%) [9, 53]. The difference in CFR is not only related to age, rather other factors such as. Occupation, gender, and clinical comorbid could be contributed to high CFR in the old age group. A better method to preventing possible misconceptions about age effect on CFR in COVID-19 patients direct age adjustment could be a solution.
Several factors could affect on mortality of COVID-19 in different settings due to health system capacity, age variation, the burden of chronic diseases, perception regarding COVID-19, and other unknown factors. For instance, the majority of COVID-19 confirmed cases in Italy are in old proportion. Moreover, most deaths due to COVID-19 in Italy are among geriatric, male patients with comorbidity [9]. In addition, the number of symptoms the cases shown is probably affected by death due to COVID-19. For example, some patients have only one or three main symptoms of COVID-19, but some patients reveal more than three symptoms which most probably affects the death due to COVID-19. Thus, advanced, in-depth analyses are required to explore the effect of the number of signs on fatalities associated with COVID-19.
Prior findings suggested that CFR of COVID-19 seems to be less deadly compared to Bird flu, Ebola, SARS, and MERS, However, it becomes a global economic and public health concern [47, 54]. In most patients, COVID-19 shows mild symptoms, which hid the burden of the disease and facilitate transmission in the community rapidly [47]. Thus, media should play a significant role in enhancing health literacy because the unique characteristics of COVID-19 make the general community at risk. Some undetected or delayed cases could probably lead to underestimation of CFR of COVID-19. Underestimation could be linked to the level of the general public and politicians’ preparedness and mitigation.
Conclusions
The pooled estimate CFR of COVID-19 in this review is considerably high and differs between different patient groups. The CFR was higher in patients admitted in ICU and older than 50 years. Moreover, the present review results highlighted the need for transparency in testing and reporting policies and denominators used in CFR estimation. It is also necessary to report the case’s age, sex, and comorbidity distribution of all patients, which is essential in comparing the CFR among different population segments.
Figures and tables
Acknowledgements
Funding sources: this research did not receive any spe-cific grant from funding agencies in the public, commer-cial, or not-for-profit sectors.
Footnotes
Ethics statement
Ethics clearance was not sought because this review was based on published articles.
Conflict of interest statement
The authors declare no conflict of interest.
Authors’ contributions
YA and MS: conception of the idea, data analysis, Manuscript writing, HHT, AAGH and MJ: searching, data extraction, manuscript writing. All authors read and approved the final manuscript.
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