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, extreme tiredness (lethargy), and sometimes coma. Patients may also experience abnormal eye movements, upper body weakness, muscule pain, tremors, neck rigidity, and behavioral changes including psychosis.
    