Infectious agents continue to cause significant morbidity and mortality despite advances in vaccines, antibiotics, antivirals, and infection control strategies. Much of our understanding of pathogen biology and disease comes from direct clinical observations in affected patients. However, there are limitations to studying infectious diseases directly in humans; as a result, the field of infectious disease research has relied on mouse, rat, hamster, guinea pig, ferret, and non-human primate models to elucidate the host response to specific pathogens. Such animal models are important tools for studying the pathogenesis of infections and for the preclinical evaluation of vaccine and therapeutic efficacies. The dominance of the mouse as a model system is driven by their relatively low cost, ease of handling, and genetic amenability that allows for the development of humanized and genetically modified mice to study infectious diseases.