Studying the interactions between enteric pathogens and their environment is important to improving our understanding of their persistence and transmission. However, this remains challenging in large part because of difficulties associated with tracking pathogens in their natural environment(s). In this study, we report a fluorescent labeling strategy which was applied to murine norovirus (MNV-1), a human norovirus surrogate, and hepatitis A virus (HAV). Specifically, streptavidin-labeled Quantum dots (Q-Dots) were bound to biotinylated capsids of MNV-1 and HAV (bio-MNV-1 and bio-HAV); the process was confirmed by using a sandwichtype approach in which streptavidin-bound plates were reacted with biotinylated virus followed by a secondary binding to Q-Dots with an emission range of 635 to 675 nm (Q-Dots 655). The assay demonstrated a relative fluorescence of 528 ؎ 48.1 and 112 ؎ 8.6 for bio-MNV-1 and control MNV-1, respectively. The biotinylation process did not impact virus infectivity, nor did it interfere with the interactions between the virus and host cells or model produce items. Using fluorescent microscopy, it was possible to visualize both bio-HAV and bio-MNV-1 attached to the surfaces of permissive mammalian cells and green onion tissue. The method provides a powerful tool for the labeling and detection of enteric viruses (and their surrogates) which can be used to track virus behavior in situ.Over the last 2 decades, production and consumption of fresh fruits and vegetables have increased dramatically, with an accompanying rise in the number of produce-associated foodborne disease outbreaks (12). It is clear from review of the CDC Food-borne Disease Outbreak database (1996 to 2006; available at: http://www.cdc.gov/foodborneoutbreaks/outbreak _data.htm) that the human noroviruses (HuNoV) are the leading cause of produce-associated food-borne disease. Although most HuNoV outbreaks are small and limited in scope, vegetable salads and berries are notable vehicles (8,11,17,18). Hepatitis A virus (HAV) is the other human enteric virus of concern in fresh produce, and several high-profile outbreaks have occurred in association with HAV-contaminated strawberries and green onions in the last decade (9, 21).Little is known about the behavior of the enteric viruses in fresh produce items although virus persistence in such products is well documented (reviewed by Papafragkou et al. [14]). It is likely that a complex set of physicochemical interactions governs such persistence, which may be associated with attachment and/or internalization of the virus in the produce item(s). Unfortunately, there are no known means by which to visualize the HuNoV and HAV in situ in order to study such purported virus-surface interactions or other mechanisms by which these viruses persist in fresh produce. In the only study of its kind, Chancellor et al. (5) used fluorescent microspheres as a surrogate to examine the uptake of HAV into green onions. The fluorophores were observed microscopically on the surface and within the green o...