Predicting the Spread of SARS-CoV-2 in Italian Regions: The Calabria Case Study, February 2020-March 2022

Abstract

Despite the stunning speed with which highly effective and safe vaccines have been developed, the emergence of new variants of SARS-CoV-2 causes high rates of (re)infection, a major impact on health care services, and a slowdown to the socio-economic system. For COVID-19, accurate and timely forecasts are therefore essential to provide the opportunity to rapidly identify risk areas affected by the pandemic, reallocate the use of health resources, design countermeasures, and increase public awareness. This paper presents the design and implementation of an approach based on autoregressive models to reliably forecast the spread of COVID-19 in Italian regions. Starting from the database of the Italian Civil Protection Department (DPC), the experimental evaluation was performed on real-world data collected from February 2020 to March 2022, focusing on Calabria, a region of Southern Italy. This evaluation shows that the proposed approach achieves a good predictive power for out-of-sample predictions within one week (R-squared > 0.9 at 1 day, R-squared > 0.7 at 7 days), although it decreases with increasing forecasted days (R-squared > 0.5 at 14 days).

Keywords: COVID-19; Calabria; Italy; SARIMA; SARS-CoV-2; epidemiology; forecasting; time series regression models.

Figure 1

Proposed approach steps.

Figure 2

Workflow of the predictive modeling step.

Figure 3

SARIMA model diagnostics.

Figure 4

Calabria epidemiological data: (A) new positive cases; (B) total amount of deaths; (C) hospitalized patients with symptoms and (D) in intensive care.

Figure 5

COVID-19 estimated $R_t$ in Calabria over a 7-day moving average, 24 February 2020–27 March 2022.

Figure 6

Data tests: (A) Box–Cox transformed data; (B) Box–Cox transformed and differentiated data.

Figure 7

Out-of-sample 14-days prediction of daily new COVID-19 cases in Calabria with SARIMA model.

Figure 8

Pooled $R^2$ scores of the 14-days out-of-sample forecast of COVID-19 new daily cases in Calabria (Italy) with SARIMA model.