Measles virus: an unwanted variant causing hydrocephalus.

Mutagenization of measles virus with proflavine produced a temperature-sensitive mutant capable of inducing hydrocephalus following intracranial inoculation of newborn hamsters. Hydrocephalus was not produced by the parental strain or by other measles virus mutants. Thus, mutants can be the causative agents of disease not associated with the parental strain. The results dictate caution in the use and distribution of experimentally induced virus variants.