A Simple Method of Finding an Approximate Pattern of the COVID-19 Spread

We are going to show that the pattern of spread of COVID-19 outside China is not monotonic. We have considered the data outside China because we are going to study the data starting from March 21, and by that time the spread had almost come to a stop in China. We have used for our analysis data on total cases outside China till April 25, 2020, and data from April 26 to April 30 for comparison of forecasts and observed values. Right from the beginning the spread pattern was nonlinear, and by the end of the third week of March the nonlinearity became nearly exponential. The exponential pattern thereafter has changed by around March 28, April 5, April 11 and April 18. Since March 21, the spread is following a nearly exponential pattern of growth changing observably at almost regular intervals of seven days. It is but natural that at some point of time the countries that had been contributing in observably large numbers to the total cases would start to show diminishing growth patterns. Therefore long term forecasts using our method would give us slightly overestimated results. However, for short term forecasting our simple method does work very well when we consider the total number of cases in the world and not in any particular country.