Rinderpest virus spreads when healthy, susceptible animals are exposed to infected droplets, either in the breath of a sick animal or in its virus-rich secretions or excretions. As the droplets are large and short-lived, the contact between sick and healthy animals must be close for transmission to occur.
Attenuated vaccine strains of rinderpest virus do not spread because they are not released into the expired air or in the faeces, having lost their epitheliotrophism.
On rare occasions, transmission has allegedly occurred through indirect contact with contaminated bedding, fodder or water. An analysis of valid records of virgin-soil epizootics from 1851 to 1950, however, clearly revealed that all instances were traceable to the importation of live animals. In short, the most likely source of a fresh focus is a newly arrived live animal.
Controlled experiments have shown that pigs also acquire infection through eating uncooked infected meat scraps. However, the practical significance of this mode of transmission is not clear.