Epidemiology, Transmission, Risk Factors, and International Responses of Coronavirus Disease 2019: A Comprehensive Review

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused a worldwide pandemic. The first reports of patients with COVID-19 were provided to World Health Organization on December 21, 2019 and were presumably associated with seafood markets in Wuhan, China. As of October 25, 2020, more than 42 million cases have been confirmed worldwide, with more than 1.1 million deaths. Asymptomatic transmission contributes significantly to transmission, and clinical features are non-specific to the disease. Thus, the diagnosis of COVID-19 requires specific viral RNA testing. The disease demonstrates extensive human-to-human transmissibility and has infected healthcare workers at high rates. Clinical awareness of the epidemiology and the risk factors for nosocomial transmission of COVID-19 is essential to preventing infection. Moreover, effective control measures should be further identified by comprehensive evaluation of hospital and community responses. In this review, we provide a comprehensive update on the epidemiology, presentation, transmission, risk factors, and public health measures associated with COVID-19. We also review past insights from previous coronavirus epidemics [i.e., severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS)] to suggest measures to reduce transmission.