When a fever strikes in the developing world, the immediate concern may be whether it is the common flu or something much worse that requires quarantine. To facilitate diagnosis in remote, low-resource settings, researchers at MIT have developed a paper-based device that changes color, depending on whether the patient has Ebola, yellow fever, or dengue fever. The diagnostic device can detect the viral hemorrhagic fevers in about ten minutes. It has silver nanoparticles of different colors that indicate different diseases. The device relies on lateral flow technology, which is used in pregnancy tests. Until now, no one has applied a multiplexing approach, using multicolored nanoparticles, to simultaneously screen for multiple pathogens.