An ARIMA Model to Forecast the Spread and the Final Size of COVID-2019 Epidemic in Italy

Coronavirus disease (COVID-2019) is a severe ongoing novel pandemic that is spreading quickly across the world. Italy, that is widely considered one of the main epicenters of the pandemic, has registered the highest COVID-2019 death rates and death toll in the world, to the present day. In this article I estimate an autoregressive integrated moving average (ARIMA) model to forecast the epidemic trend over the period after April 4, 2020, by using the Italian epidemiological data at national and regional level. The data refer to the number of daily confirmed cases officially registered by the Italian Ministry of Health (www.salute.gov.it) for the period February 20 to April 4, 2020. The main advantage of this model is that it is easy to manage and fit. Moreover, it may give a first understanding of the basic trends, by suggesting the hypothetic epidemics inflection point and final size. Highlights ARIMA models allow in an easy way to investigate COVID-2019 trends, which are nowadays of huge economic and social impact. These data may be used by the health authority to continuously monitor the epidemic and to better allocate the available resources. The results suggest that the epidemic spread inflection point, in term of cumulative cases, will be reached at the end of May. Further useful and more precise forecasting may be provided by updating these data or applying the model to other regions and countries.