Tollulah Oni, right, running with teammates during an event at the International Conference on Sustainable Urban Mobility in Lagos, Nigeria, in 2025. Credit: LAMATA/The 2025 International Conference on Sustainable Urban Mobility Run

In 2016, public-health physician Tolullah Oni was jogging through the streets of Dakar when she saw someone doing push-ups in the middle of a busy roundabout. Cars were puffing fumes around him as the Sun baked down. As a physician, she knew that this had health implications.

More than half of the global population now lives in urban areas, but many cities are not conducive to human health and well-being. Oni, who is a researcher at University of Cambridge, UK, describes herself as an urban epidemiologist whose patients are cities. She works with colleagues around the world to diagnose and treat ‘sick’ cities with the goal of improving the health and quality of life of their inhabitants.…