An encephalitis that was epidemic between 1915 and 1926; symptoms include paralysis of the extrinsic eye muscle and extreme muscular weakness WordNet 3.0 & Open English WordNet

Encephalitis lethargica is an atypical form of encephalitis. Wikipedia

Atypical form of encephalitis Wikidata

Especially, African sleeping sickness, an endemic infectious disease of humans and animals in tropical Africa, caused by a parasitic trypanosome, transmitted by the tsetse fly and characterized by fever, severe headache, joint pains and lymph node swelling in the early stages, followed by a neurological phase of extreme weakness, sleepiness, and deep coma leading to death. Wiktionary

Infectious disease. Wiktionary (translation)