Encephalitis and Lethargic encephalitis

Encephalitis noun - Inflammation of the brain usually caused by a virus; symptoms include headache and neck pain and drowsiness and nausea and fever (`phrenitis' is no longer in scientific use).

Lethargic encephalitis and encephalitis are semantically related. In some cases you can replace phrase "Lethargic encephalitis" with "Encephalitis", this terms are similar.

Lethargic encephalitis noun - An encephalitis that was epidemic between 1915 and 1926; symptoms include paralysis of the extrinsic eye muscle and extreme muscular weakness.

Encephalitis and lethargic encephalitis are semantically related. You can use "Encephalitis" instead a noun phrase "Lethargic encephalitis".