Studies on parainfluenza type 2 and 4 viruses obtained from patients with common colds.

Four agents which were obtained from adults with common colds were cultivated and identified-one was influenza type B and the others were parainfluenza viruses of types 2 and 4. Their cultivation was assisted by the use of organ cultures of human embryo tracheal or nasal epithelium. They infected and caused typical common colds in volunteers.