How do you smell? African giant pouched rats are plentiful in Tanzania, and so is tuberculosis. One quarter of the world’s 9 million annual diagnoses of treatable TB occur in Africa, and the standard detection method is only 60 percent effective — even less so when patients also have HIV. But last year, rats sniffed cough and spit samples, successfully identifying 9,127 infected people previously told by health clinics they were TB free. Meanwhile, experimental studies are looking into whether dogs can sniff out cancer in a trend that may replace ineffective clinical procedures with whiskered whiffers.