Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Schistosomiasis ?
    ### Response:
    Schistosomiasis is a disease caused by parasitic worms. Although the worms that cause schistosomiasis are not found in the United States, more than 200 million people are infected worldwide. Infection occurs through contact with contaminated water. The parasite in its infective stages is called a cercaria.
    