The frantic, high-tech fight to stop climate-fueled dengue fever

The first patient arrived just over two years ago. January was supposed to be a slow month at Santa Rosa, a hospital nestled in the middle-class Pueblo Libre district of Lima, Peru. The sprawling metropolis of 10 million can feel eerily empty at the height of summer, when some families flee the city and many others flock to the beach.

The patient, a woman in her early 20s, had traveled 270 miles with her mother from their home in the central Peruvian jungle. She had a high fever and unbearable stomach pain ...