The Use of Triangular Norms in Epidemiological Models: A Comparative Study Using COVID-19 Data

In this manuscript we use triangular norms to model contact between susceptible and infected individuals in the susceptible-infected-recovered (SIR) epidemiological model. In the classical SIR model, the encounter between susceptible and infected individuals is traditionally modeled by the product of their densities (
$SI$
). That is, the encounter is modeled by the product t-norm. We use the COVID-19 data and extended versions of the SIR model whose encounters are modeled by four triangular norms, namely, product, minimum, and Frank and Hamacher t-norms, to analyze the scenario in three countries: 1) Germany; 2) Italy; 3) Switzerland. We compare all versions of the SIR model based on these triangular norms, and we analyze their effectiveness in fitting data and determining important parameters for the pandemic, such as the basic and effective reproduction number. In addition, Frank and Hamacher triangular norms present an auxiliary parameter that can be interpreted as an indicator of control measure, which we show to be important in the current pandemic scenario.