This year’s World Health Day theme—Urbanization and Health—reflects the rising number of people living in cities around the world. In 2007, the world’s urban population surpassed 50% for the first time in history, and this proportion is growing—by 2050, it’s estimated to exceed 70%.

Low- and middle-income countries are the most affected by demographic changes, bearing 80% of the world’s burden of disease and the highest attrition rates of doctors and nurses to other parts of the world. Meanwhile, between 1995 and 2005 alone, the urban population of developing countries grew by an average of 1.2 million people per week, or around 165,000 people every day. Inarguably, these trends influence the accessibility, quality, and cost of long-term health care in urban and rural communities, alike.

For 30 years, IntraHealth has balanced its work in extending services to hard-to-reach and often underserved rural populations with increasing attention to urban health issues and disparities. But every city is different, with likely as many variables for change—housing infrastructure, physical climate, political stability, availability of jobs—as there are health disparities. Recognizing this, we’re seizing World Health Day, April 7, 2010, to ask how can we, collectively bring new thinking to those challenges that urbanization is bringing to global health?