English: Principle routes of canine distemper virus (CDV) infection and transmission in hosts. a Infected DCs and alveolar macrophages progress to the local draining lymph node, where they interact with and infect T-cells and B-cells through CD150 that is also expressed on their cell surface. These infected cells further spread to secondary lymphoid organs, causing a secondary viremia. b At the final stages of infection, shedding of infected lymphocytes to distal site of the respiratory tract. These infected lymphocytes interact with the epithelial cell receptor nectin-4, located in the adherent junctions on the basolateral surface of the epithelial cell. Infection in the airway epithelium results in the virus assembly and the release of virions into the airway lumen of the infected lung. c CDV can infect the CNS in some instances and it has been suggested that the receptor nectin-4 has an important role in this infection.