Human norovirus causes approximately 20 times more gastrointestinal illnesses than any other pathogenic agent in the U.S., and the annual cost associated with these illnesses is estimated to be in the billions (US $). Despite this, human norovirus is not included in most drinking water and water reuse regulations. This is largely due to the fact that Human Norovirus cannot be cultured in vitro, that is, no cell line is available to count the number of infective viruses in samples. As a result, the scientific community does not know the extent of disinfecting treatments necessary to inactivate human norovirus. Our current understanding of necessary disinfection doses and disinfection kinetics relies primarily on surrogate virus studies; this is despite the fact that research has indicated that the surrogate viruses respond differently to disinfectants than human norovirus. The drinking water and water reuse fields are in desperate need of accurate human norovirus disinfection data so that water treatment guidelines and compliance levels can be established. Deaths caused by human norovirus are especially common in the developing world; improved human norovirus disinfection would therefore have positive impacts on impoverished populations. Ultimately, the research will lead to improved disinfection strategies, which could ultimately prevent millions of norovirus cases and save thousands of lives. The PIs will incorporate this project into their ongoing broader impact activities, including summer research activities for underprivileged students and drinking water projects in developing countries.
In this project, the PIs propose to establish the first disinfection curves of human norovirus based on infectivity. Dr. Christiane Wobus of the University of Michigan recently discovered an immune deficient mouse strain that is infected by human norovirus, and thus represents the first small animal model for human norovirus. This mouse model allows us for the first time to develop dose-response curves for the human norovirus with disinfectants (chemicals commonly used in water and wastewater treatment). These disinfection dose-response curves are critical; however, routine monitoring cannot be based on the mouse model, and must instead rely on cheaper techniques available to a much larger group of scientists and practitioners. Once disinfection curves of norovirus have been established in this project, we will use them to calibrate a method that estimates human norovirus inactivation based on quantitative PCR (qPCR). Scores of studies have reported that qPCR cannot be used to determine virus infectivity; however our research has overturned this notion by showing that qPCR analysis can, in fact, accurately measure virus inactivation, provided that the results are analyzed within the correct theoretical framework. Coupling the mouse model disinfection data with the extrapolation method will lead to a simple and robust qPCR assay that effectively tracks human norovirus infectivity levels without the need for cell cultures or the mouse models. This project aims to increase the safety of our nation's water and food supplies and reduce the associated economic burden of human norovirus illnesses. In particular, results from: Task 1 of this project will, for the first time, define specific UV doses necessary to achieve desired levels of human norovirus inactivation. Task 2 will introduce a simple and inexpensive qPCR assay to track human norovirus inactivation. The PIs are confident that the outputs from this project will be transformative for a number of industries for which human norovirus is a major concern including drinking water, wastewater, food, and hospital.
