Laboratory testing has played a pivotal role throughout the coronavirus disease 2019 (COVID-19) pandemic, exemplifying the importance of in vitro diagnostics in addressing public health threats posed by outbreaks of infectious diseases. This article aims to present key insights from our expertise, derived from evidence gathered during the COVID-19 pandemic, to inform strategies for managing future infectious challenges. Current scientific evidence underscores that patient sample testing not only allows to diagnose an acute severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, but also supports outbreak prediction, improved control measures, anticipation of pressure on the healthcare system, mitigation of adverse clinical outcomes, and early detection of emerging SARS-CoV-2 variants. Additionally, wastewater monitoring has emerged as a powerful tool for forecasting disease burden, including both prevalence and severity. Collectively, these findings underscore the value of diagnostic testing and wastewater surveillance in guiding healthcare planning and optimizing resource allocation during the COVID-19 pandemic, offering a valid framework to be applied to future public health threats, especially to any potential outbreak of "Disease X" that may emerge in the future.