Introduction: Rapid and accurate diagnostic approaches are essential for impeding the spread of infectious diseases. This review aims to summarize current progress of clustered regularly interspaced short palindromic repeats (CRISPR)‐associated (Cas) systems in the applications for diagnostics of infectious diseases including the ongoing COVID-19 epidemic. Areas covered: In this review, we discuss class 2 CRISPR-Cas biosensing systems-based diagnostics in various emerging and reemerging infectious diseases, CRISPR-Cas systems have created a new era for early diagnostics of infectious diseases, especially with the discovery of the collateral cleavage activity of Cas12 and Cas13. We mainly focus on different CRISPR-Cas effectors for the detection of pathogenic microorganisms as well as provide a detailed explanation of the pros and cons of CRISPR-Cas biosensing systems. In addition, we also introduce future research perspectives. Expert commentary: However, further improvement of newly discovered systems and engineering existing ones should be developed to increase the specificity, sensitivity or stability of the diagnostic tools. It may be a long journey to finish the clinical transition from research use. CRISPR-Cas approaches will emerge as more promising and robust tools for infectious disease diagnosis in the future.