3.3. Exponential Growth Model
The exponential growth model assumes that the onset of any outbreak follows an exponential distribution. However, due to government interventions, medical innovations, behavioural changes etc, at a later stage, the growth curve becomes flattened and rate of infections gradually reduces [54]. To identify such signs, we look at the infections in the last seven days period and the deviation of the data points from the modelled exponential curve is captured using the mean absolute percentage error metric. Based on the errors and the direction in which the actual data points are to the modelled growth curve, the countries are classified as weather they show initial sign of containment or not. Table 2 shows the results of exponential growth models for different countries and if the countries showed a sign of containment or not based on the results. Figure 2 and 3 shows actual infections for the countries and the infections predicted by its corresponding exponential growth model. The countries Brazil, Canada, Ecuador, France, Germany, India, Italy, Luxembourg, Malaysia, Pakistan, Panama, Philippines, Romania, South Africa, Spain, The United Kingdom, Turkey, and United States of America did not show any signs of initial containment as the infections in the last seven periods exceeded or followed the exponential growth model. The countries that showed initial signs of containment were Austria, Chile, China, Czechia, Denmark, Greece, Iceland, Indonesia, Iran, Ireland, Israel, Japan, Netherlands, Norway, Peru, Poland, Portugal, Qatar, Republic of Korea, Saudi Arabia, Singapore, Slovenia, Switzerland, and Thailand.
Table 2. Exponential Growth Model & Sign of Initial Containment