The present invention relates to microfluidic fluidic systems and methods for the in vitro modeling diseases of the lung and small airway. In one embodiment, the invention relates to a system for testing responses of a microfluidic Small Airway-on-Chip infected with one or more infectious agents (e.g. respiratory viruses) as a model of respiratory disease exacerbation (e.g. asthma exacerbation). In one embodiment, this disease model on a microfluidic chip allows for a) the testing of anti-inflammatory and/or anti-viral compounds introduced into the system, as well as b) the monitoring of the participation, recruitment and/or movement of immune cells, including the transmigration of cells. In particular, this system provides, in one embodiment, an in-vitro platform for modeling severe asthma as “Severe Asthma-on-Chip.” In some embodiments, this invention provides a model of viral-induced asthma in humans for use in identifying potentially effective treatments.