The ability to detect infectious viruses is of critical importance in medical diagnostic and environmental/agricultural protection. Current methods to assess the presence of infectious viruses are based on mammalian cell culture and rely on the production of visible cytopathic effects (CPE). Depending on the specific virus type and concentration in the sample, it may take several days or weeks for CPE to appear. In this talk, I will discuss several FRET-based approaches recently developed in my lab for real-time monitoring of viral infection. Quantum dot-based molecular probes were designed to detect the presence of viral RNAs or proteases as an indicator of viral infection. For intracellular delivery, a cell-penetrating TAT peptide was appended to the probes to enable real-time monitoring of viral infection in living cells. Fluorescence microscopy and flow cytometry were used to directly visualize infected cells and to subsequently follow virus spread in situ. As an added benefit, the specific nature of these probes also enables their utility as a sensitive agent for viral inhibitors discovery. Some progress in this area will be discussed.