Modeling infectious disease trend using Sobolev polynomials Rolly Czar Joseph Castillo (a*), Victoria May Mendoza (b,a), Jose Ernie Lope (a), and Renier Mendoza (a)
a) Institute of Mathematics, University of the Philippines Diliman
*rtcastillo1[at]up.edu.ph
b) Natural Sciences Research Institute, University of the Philippines Diliman
Abstract
Trend analysis plays an important role in infectious disease control. An analysis of the underlying trend in the number of cases or the mortality of a particular disease allows one to characterize its growth. Trend analysis may also be used to evaluate the effectiveness of an intervention to control the spread of an infectious disease. However, trends are often not readily observable because of noise in data that is commonly caused by random factors, short-term repeated patterns, or measurement error.
In this paper, a smoothing technique that generalizes the Whittaker-Henderson method (WHM) to infinite dimension and whose solution is represented by a polynomial is applied to extract the underlying trend in infectious disease data. The solution is obtained by projecting the problem to a finite-dimensional space using an orthonormal Sobolev polynomial basis obtained from Gram-Schmidt orthogonalization procedure and a smoothing parameter computed using the Philippine Eagle Optimization Algorithm, which is more efficient and consistent than a hybrid model used in earlier work. Because the trend is represented by the polynomial solution, extreme points, concavity, and periods when infectious disease cases are increasing or decreasing can be easily determined. Moreover, one can easily generate forecast of cases using the polynomial solution. This approach is applied in the analysis of trends, and in forecasting cases of COVID-19.
Keywords: Whittaker-Henderson method, data smoothing, Sobolev space
