Professor Fan's NSF Collaboration Grant award, over $700K, is joint with the University of Wisconsin-Madison. The funds will support the study of stochastic reaction-diffusion equations on metric graphs and spatially-resolved dynamics of virus infection spread.This award supports the development of new mathematical tools and biological experiments that are essential to understanding the mechanisms of virus spread and extinction. A new framework, to enable an integrated experimental-mathematical study, will be developed to control the spatial distribution of the host cell population and to quantify how such spatial structure affects viral evolution and decay. The project has basic research, medical, and public health impact, since the analytical and experimental methods can be extended to elucidate mechanisms of infection spread by viruses of public health importance, including influenza A virus, Zika virus, and coronaviruses. As an interdisciplinary study, the research will cross-train biologists, engineers, and mathematicians, contributing significantly to workforce development. Broader objectives include increased participation and diversity in STEM fields while promoting a broader understanding of science and technology by the public through wide dissemination.Professor Fan's research is also now supported by a $45K award from the Hong Kong Research Grant council. His project investigates stochastic modeling of the spatial transmissions of viruses and defective interfering particles.The award enables international collaboration and training of students in STEM fields. The project goal is to develop stochastic simulation schemes for delayed differential equations to study virus spread in two-dimensional domains.