Keele Research Repository

Background and aims
Realizing the transmission potential and the magnitude of the coronavirus disease 2019 (COVID-19) aids public health monitoring, strategies, and preparation. Two fundamental parameters, the basic reproduction number (R0) and case fatality rate (CFR) of COVID-19, help in this understanding process. The objective of this study was to estimate the R0 and CFR of COVID-19 and assess whether the parameters vary in different regions of the world.

Methods
We carried out a systematic review to find the reported estimates of the R0 and the CFR in articles from international databases between January 1 and August 31, 2020. Random-effect models and Forest plots were implemented to evaluate the mean effect size of R0 and the CFR. Furthermore, R0 and CFR of the studies were quantified based on geographic location, the tests/thousand population, and the median population age of the countries where the studies were conducted. To assess statistical heterogeneity among the selected articles, the I2 statistic and the Cochran's Q test were used.

Results
Forty-five studies involving R0 and 34 studies involving CFR were included. The pooled estimation of R0 was 2.69 (95% CI: 2.40, 2.98), and that of the CFR was 2.67 (2.25, 3.13). The CFR in different regions of the world varied significantly, from 2.49 (2.08, 2.94) in Asia to 3.40 (2.81, 4.04) in North America. We observed higher mean CFR values for the countries with lower tests (3.15 vs 2.16) and greater median population age (3.13 vs 2.27). However, R0 did not vary significantly in different regions of the world.

Conclusions
An R0 of 2.69 and a CFR of 2.67 indicate the severity of the COVID-19. Although R0 and CFR may vary over time, space, and demographics, we recommend considering these figures in control and prevention measures.