I called Bradley and asked if the leish had really died out or if it was still around. “I’m sure it hasn’t gone away,” she said. “It’s smoldering somewhere out there, quietly cycling in nature,” waiting for the right combination of circumstances to break out again. When she and her team mapped leish cases in the United States over time, they revealed an inexorable spread northeastward across Texas and Oklahoma, aiming for other states in a northeasterly direction. Why? Her answer was immediate: “Climate change.” As the United States becomes warmer, she said, the ranges of the sand fly and the
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