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