For generations, epidemiologists have tracked how disease moves through populations while sociologists have mapped how inequality shapes human vulnerability — yet these two disciplines rarely shared a common language. A research team led by Brandon Ogbunu of Yale and the Santa Fe Institute has now built a bridge between them, introducing a mathematical metric that gives social determinants of health a precise, quantifiable place inside the models that guide public health decisions. The insight is as old as it is urgent: disease does not spread through biology alone, but through the conditions