Exponential damping key to successful containment of COVID-19 outbreak

Due to the excessively high capability of human-to-human transmission, the 2019 novel coronavirus disease (COVID-19), first reported in Wuhan of China, has rapidly spread to the entire nation and beyond, and has now been declared a global public health emergency. Understanding the transmission pattern of the virus and the effect of control measures on the transmission, is crucial to improving the national and international disease control effectiveness. We here propose a simple model based on the exponential infectious growth but with a time-varying, largely damping, transmission rate. This model provides an excellent fit to the existing data and, we think, has largely captured the transmission pattern of the COVID-19 outbreak under a variety of intervention and control measures. Successful control measures, such as in China and South Korea, have resulted in an exponentially damping dynamics of the viral spread. Such exponential damping, therefore, could be used as a measure of control effectiveness, as also shown in the data of the 2003 severe acute respiratory syndrome (SARS). Our model suggests that the COVID-19 outbreak is currently accelerating worldwide with the exponential damping yet to emerge. Consistent with the message from the World Health Organisation (WHO), we thus strongly suggest all countries to take active measures to contain this global pandemic.