Cross-Country Learning for National Infectious Disease Forecasting Using European Data

Accurate forecasting of infectious disease incidence is critical for public health planning and timely intervention. While most data-driven forecasting approaches rely primarily on historical data from a single country, such data are often limited in length and variability, restricting the performance of machine learning (ML) models. In this work, we investigate a cross-country learning approach for infectious disease forecasting, in which a single model is trained on time series data from multiple countries and evaluated on a country of interest. This setting enables the model to exploit shared epidemic dynamics across countries and to benefit from an enlarged training set. We examine this approach through a case study on COVID-19 case forecasting in Cyprus, using surveillance data of European countries. We evaluate multiple models and analyse the impact of the lookback window length and cross-country 'data augmentation' on multi-step forecasting performance. The results show that combining data from other countries can lead to consistent improvements over models trained solely on national data. Although the focus is on Cyprus and COVID-19, the framework and findings provide promising insights for infectious disease forecasting in settings with limited national data.