Experimental parainfluenzavirus infection in mice: fatal illness with atrophy of thymus and spleen in mice caused by a variant of parainfluenza 3 virus.

Intracerebral inoculation of the YN strain of parainfluenza 3 virus was found to induce an acute fatal illness characterized by marked thymic and splenic atrophy in newborn mice. Previously we showed that the YN strain contains three distinct plaque-type variants, LT, SC, and M. Of these, the M-type variant induced this fatal illness, whereas the other two variants induced hydrocephalus.