Relationship of communicability of a Newcastle disease virus to its resistance to a respiratory inhibitor.

Newcastle disease virus resistant to a nonspecific inhibitor in nasal mucus of normal chickens differed in several important properties from the inhibitor-sensitive virus stock from which it was derived. Aerosols from chickens infected with the inhibitor-resistant virus were infectious for susceptible chickens, and those from chickens infected with the inhibitor-sensitive virus were not infectious.