Orphan virus
An orphan virus is a virus that is not associated with a disease but may possess pathogenicity.
Gilbert Dalldorf, a pathologist who showed that Coxsackie viruses paralyze mice but not humans, indicated that the term ‘orphan’ was created "in a moment of conviviality" by a group of virologists.
Many enteroviruses are referred to as ECHO, enteric [cytopathic human orphan virus]es, because they were originally not associated with any disease.