November 1, 20235:20 AM ET Max Barnhart Sand flies carry the protozoan parasites that spread leishmaniasis. It was thought to be a disease of tropical climates, but leishmaniasis-causing parasites have now been found living and circulating in the United States.Science Photo Library Back in 2014, dermatologist Bridget McIlwee saw a 3-year-old patient in central Texas...
