Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Encephalitis Lethargica ?
    ### Response:
    Encephalitis lethargica is a disease characterized by high fever, headache, double vision, delayed physical and mental response, and lethargy. In acute cases, patients may enter coma. Patients may also experience abnormal eye movements, upper body weakness, muscular pains, tremors, neck rigidity, and behavioral changes including psychosis.
    