A parasite called cyclosporiasis, which can cause explosive and watery bowel movements, has infected nearly 2,000 people in the United States this year. | Paige Vickers/Vox; Getty Images As if we needed one more thing to worry about so soon after the hantavirus scare, there is a new public health threat for Americans to contend with: a rapidly escalating outbreak of, of all things, diarrhea. It’s a parasite called cyclosporiasis. It can cause explosive and watery bowel movements — and it is wr