Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Post-Polio Syndrome ?
    ### Response:
    Post-polio syndrome (PPS) is a condition that affects polio survivors many years after recovery from an initial attack of the poliomyelitis virus. PPS is characterized by a further weakening of muscles that were previously affected by the polio infection. The most common symptoms include slowly progressive muscle weakness, fatigue (both general and muscular), and a decrease in muscle size (muscular atrophy).
    