This study aimed to identify and summarize the existing evidence on epidemiological characteristics of SARS-CoV-2 and the effectiveness of control measures.
This was a systematic review of the published literature and preprints on the coronavirus disease (COVID-19) outbreak. Articles included those covering transmission dynamics, severity, susceptibility and control measures.The search was performed on PubMed on 21 February 2020.
41 articles were included in the review. Findings suggest that the true size of the epidemic is much larger than what has been reported worldwide, though these figures largely depend on the effectiveness of the control measures. The outbreak is growing fast with an infected individual infecting two to three other persons on average and doubling in size every 3 to 7 days.
These articles additionally suggest that:
- It takes about 3-7 days for the epidemic to double in size.
- The basic reproduction number ranges from 1.9 to 6.5.
- The incubation period ranges from 3 to 6 days, the mean (or median) is most likely to be around 5 days on average, which is similar to that of other coronaviruses, such as SARS-CoV (4.4 days).
- The true case fatality risk is yet unknown, but current model-based estimates ranged from 0.3% to 1.4% for outside China. Modeling-based estimates of the CFR vary largely between studies, but overall are found to be less severe than other coronaviruses, such as SARS-CoV (9.6%) and MERS-CoV (34.5%). According to the latest statistics, the observed mortality rate of COVID-19 is estimated to be around 4.8% worldwide.
- Control measures such as quarantine, travel restrictions, and airport screening for travelers have been widely implemented to contain the spread of infections. The effectiveness of these containment measures in controlling the outbreak, however, remains inconclusive. The effectiveness of control measures could be hampered by a significant portion of asymptomatic patients (17.9%, 95% CrI: 15.5–20.2%) and pre-symptomatic transmission (12.1%).
There is an urgent need for rigorous research focusing on the mitigation efforts to minimize the impact on society.