Newcastle disease, pneumoencephalitis, acute viral disease of domestic poultry. Newcastle disease is characterized by sneezing, coughing, and nervous behavior. Affected birds may show tremors, circling, falling, twisting of the head and neck, or complete paralysis. Mortality reaches 90% in very young birds but adult mortality is very low. Among affected laying hens, egg quantity and quality drop sharply at first but usually return to former levels within four to eight weeks. In humans the virus causes only a temporary conjunctivitis. The disease can be controlled in poultry by sanitary management and isolation of flocks, and by live-virus and inactivated vaccines administered by injection or in eye-drops, aerosol sprays, or drinking water.