"This proposal would bring a mathematical epidemiologist from the U.S. to the University of Lyon (France) to collaborate with researchers in the Biometry and Evolutionary Biology Laboratory in research on the nosocomial transmission of rotavirus in pediatric and other hospital wards. Because of inadequate sterilization and pathogen resistance to antibiotics, healthcare workers and hospital equipment act as vectors to spread these infections from one patient to another, causing thousands of deaths each year, especially among children under five years of age. This project proposes to develop and analyze a sequence of mathematical models describing the transmission dynamics, beginning with deterministic compartmental models which describe the average spread of infections at the hospital level and progressing to stochastic and network-based models which take into account individual variations in transmission within small populations such as wards, and the structure of infectious contacts that connects multiple wards through workers and equipment moving from one ward to another. The project also includes two methodological components: one which will compare epidemiological indices of infection transmission such as the basic reproductive number, to see which best capture the effects of contact structures (how potential infection events occur), and another which applies uncertainty and sensitivity analyses in order to derive a measure of confidence in the results. This interdisciplinary collaboration, broad both in the fields of expertise from which it draws and in the spectrum of modeling approaches it uses, aims to play an important role in the context of public health: by putting predictive tools at the disposal of the community of physicians, it aligns with the public health strategy of the European Community in improving the capability to respond to significant public health threats."