We previously described a mathematical model to simulate the course of the COVID-19 pandemic and try to predict how this outbreak might evolve in the following two months when the pandemic cases will drop significantly. Our original paper prepared in March 2020 analyzed the outbreaks of COVID-19 in the US and its selected states to identify the rise, peak, and decrease of cases within a given geographic population, as well as a rough calculation of accumulated total cases in this population from the beginning to the end of June 2020. The current report will describe how well the later actual trend from March to June fit our model and prediction. Similar analyses are also conducted to include countries other than the US. From such a wide global data analysis, our results demonstrated that different US states and countries showed dramatically different patterns of pandemic trend. The values and limitations of our modelling are discussed.

Since the early reports of COVID-19 cases in China in late January 2020 (1-2), the worst pandemic in 100 years has spread to the entire globe with approximately 2.4 million diagnosed cases and over 165,000 deaths up to April 20, 2020. While scientists from various public and private groups use math and computer to simulate the course of this pandemic to try to predict how this outbreak might evolve (3), most of such analyses are either quite complicated or not publicly available. Here a simple mathematic modeling approach is taken to track the outbreaks of COVID-19 in the US and its selected states to identify the peak point of such outbreak within a given geographic population, the trend of decreasing numbers of new cases after the peak and the rough calculation of accumulated total cases in this population from the beginning to the end of June 2020. The sources of COVID-19 case data are taken from various public websites since not all the data are readily available.