Dated and potentially sensitive medical term for Hansen's disease. In modern contexts, ハンセン病 is preferred.
See also: ハンセン病
The disease once called 'leprosy' is now known as Hansen's disease.
I have seen the term 'leprosy' in history textbooks.
Full kanji form using the non-Jōyō character 癩. Less common in modern writing.
From らい (癩, 'leprosy') + 病 (びょう, 'disease'). The character 癩 is a phono-semantic compound, but the exact derivation is uncertain.