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. This involves monitoring several variables, such as air quality and temperature, and their impact on the city’s residents. Those data can inform advocacy and interventions.

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Frustrated by a lack of infrastructure on the ground in such cities, and by the struggle to connect researchers and residents, she set up the non-profit organization UrbanBetter in 2019 to support her research and advocacy. By providing training on data collection and analysis, the organization helps citizens and local researchers to diagnose their own cities and to use that evidence to lobby for change. Its research arm, the UrbanBetter Academy, has a centre in Cambridge, and its civic arm, called Cityzens Hubs, operates in 11 cities in Africa, as well as in Bogotá and Bangkok.

Oni, who was born in Nigeria, identifies as African diaspora, which she classifies as a “sixth distinct region of the African continent”. Now based in the United Kingdom, she recognizes the friction that comes with trying to treat cities that she does not live in. Oni tells Nature how she wants to create lasting virtual infrastructure through UrbanBetter that channels the diaspora’s intellectual capital back into the continent and heals sick cities.

How can a doctor diagnose and treat cities?

Cities can’t tell you that they’re sick, so you must bring the symptoms to light first. What are the lungs or air quality doing? What is happening in the green spaces? How is the city metabolizing energy? What is happening to its waste? If you don’t have the data, you don’t know whether the city is sick and in a lot of our cities, we’re not even measuring those things.

It is important that the people who are identifying the symptoms are on the ground in that city, rather than me, a professor, sitting thousands of kilometres away in Cambridge. People there are breathing the air and moving through the city. We have to equip local people with the skill set to diagnose a city. The diagnostic tests can be done by sensors and their data can be mapped.

In cities, we need treatments to be grounded in lived realities. Outsiders can assess a city and propose a solution, backed by evidence, but it might not work for many reasons. We need to include residents. They can identify priority areas and advocate for change. For example, in Nairobi, a group of Cityzens collected air-pollution data and convened their own community assembly in 2025 to identify potential solutions, such as cleaner public transport, adding trees and green spaces and reducing open burning of rubbish. These points fed directly into the government’s Nairobi City County Air Quality Action Plan.

Developing treatments for a city is a collective effort and accountability is spoon-feeding that medicine in the form of small, incremental changes so that the city can get better.

How does UrbanBetter help cities?

I set up UrbanBetter in 2019 as an experimental platform that would situate research differently by combining it with action and advocacy. We started with a US$300,000 unrestricted grant from the funding organization Unorthodox Philanthropy, which is sponsored by the Lampert Byrd Foundation based in San Francisco, California.

Each of UrbanBetter’s hubs has different strengths — Lagos works on physical activity, air pollution and heat, whereas Bogotá has done work on transport, cycling and car-free days. This means that when another city wants to work in a new area, they don’t have to reinvent the wheel.

Ahead of the 2025 Lagos City Marathon, the local Cityzens Hub partnered with World Athletics’ project Running for Clean Air. The marathon takes place in February, which is among the hottest times of year in Lagos, and the city has high levels of air pollution.

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Throughout 2025, a group of residents ran the marathon route each month, starting in the January before the marathon. They wore air-quality sensors and collected geotagged data with the UrbanBetter app. Some runners found that there was a 60% reduction in air pollution on the actual marathon day because cars were barred from the roads. These findings have informed a shift in transportation-policy implementation in the city, which is now targeting net-zero emissions by 2050. Government initiatives include increased cycling and walking, an overhaul of public transport and increased air-quality monitoring.

The Cityzens Hub then identified heat as another major issue for city dwellers, so they reached out to the UrbanBetter Academy for help analysing complex data. In 2025, researchers from UrbanBetter, local partner institutions and the Lagos Transport Authority received a £2-million [roughly US$2.6-million] grant from the biomedical funding charity Wellcome to investigate heat exposure and health risks in Lagos in a project called Hotsteppers. This is how UrbanBetter works — that research question about heat came from people on the ground raising the issue.