Malaysia Covid-19 Forecast Using Generalized Logistic Function (Updated 23-Apr-2020)

In a previous article (Read more here), a Simple Logistic Function (SLF) was chosen to model the Covid-19 growth trend in Malaysia for the 1^st phase of the Movement Control Order (MCO).  During that said period, the SLF model appeared to be adequate as the goodness-of-fit of the curve was reasonable.  However, at the end of the 2^nd phase of MCO (14-Apr-2020), the SLF model was no longer adequate to explain the development of Covid-19 in Malaysia.

A more robust model, Generalised Logistic Function (GLF) was now needed (Read more here), as suggested by some international research papers (Read more here).  There are a couple of reasons why the SLF model is inadequate to predict the growth of the Covid-19.  Firstly, the Covid-19 development was not in a closed-system.  SLF is commonly used in studying the growth of bacteria in a laboratory.  In the Covid-19 case, although MCO was implemented, it is not a true closed-system as there were leakages that impacted the growth pattern. This may include test capacity, asymptomatic patients, previous undisclosed linked clusters, and MCO violations.  Secondly, the previous model might appear good due to insufficient data points.  As time passed, more data points were available to show the actual trend of the development.

The GLF, in mathematical form, is 

The constants A, K, C, Q, B and v are determined by minimizing the sum of square of the 21-Days rate of change between the actual cumulative cases and the GLF.  Graph 1 is the cumulative of positive cases, Graph 2 is the 21-Day rate of change, and Graph 3 is the daily new cases trend.

Based on the fitted GLF, the predicted median total cases are expected to be around 6400 by the middle of June 2020, worst case 6800, and best case 6100.  This number is derived purely from a quantitative approach.  It does not factor in traffic movements (flight routes re opened), new vaccine development and other qualitative measures.  Nevertheless, the number could be reduced further if we abide by the MCO, and practice good social distancing.  As at 23-Apr-2020, the daily new cases trend is moving towards the best- case scenario. That simply means by the end of Phase 3 MCO, the daily new cases would go below 30 as depicted in Graph 3. Hopefully, then we can restart the economy.

So please Stay@Home for now!