Putting Health in Place

The famous discovery of the origin of a cholera outbreak in a London water pump in 1854 by Dr. John Snow—often regarded as the birth of both the modern city and the field of epidemiology—was achieved through a map. 

Given that, it's surprising how little we have applied geography in shaping either our knowledge of what determines health or our strategies for achieving it. This has arguably been a significant mistake in analysis. But it is certainly a mistake in strategy.


Doctor checks the heartbeat of an older Asian woman

The classic epidemiologic triad consists of (1) an agent of disease, (2) a susceptible host, and (3) the environment. Medical science has made great advances in identifying and addressing the first two—from antibiotics to genetics to advances in medical technology. We have made less progress on the third—a contextual cornucopia that includes the built environment, the social determinants of health, and local ambient conditions. 

What we have learned is that 80 percent of our health outcomes are context driven: physical environment (10%), health behaviors (30%), and social and economic factors (40%). Only the remaining 20 percent is determined by a person's genome and microbiome (the symbiotic organisms—including billions of bacteria and other microbes—that make up an individual human being) and the clinical care they receive. These first three factors are known collectively as the exposome, defined as the measure of all the exposures of an individual in a lifetime. A person's exposure begins before birth and includes inputs from environmental and occupational sources, such as climate, metals and plastics, ozone, pollution, tobacco, pesticides, infection, stress, and socioeconomic factors.


Map showing an area with diamonds of varying sizes and colors

What we have come to see is that the best way to organize and analyze that exposomic complexity is through location. Even in normal times, your ZIP code can be as important to your health outcomes as either your genetic code or your tax code. Now multiply that by an order of magnitude during a pandemic. As the Centers for Disease Control and Prevention (CDC) puts it, "Both the who and the when of disease are relative to and often dependent on the where." 

Fortunately, we now have the means to understand that where. Through an emerging geospatial mindset and the new tools of location intelligence, enhanced by artificial intelligence, we can now analyze environmental and societal complexities and their impact on our health. 

The where turns out to be the best lens for determining how to fight disease and produce public health. 

Place not only helps us understand our full health context but also shows us where and how to intervene. 

Take the current pandemic. 

  • Mapping the epidemic: The sophisticated mapping capacities developed during the West Nile, SARS, Ebola, and Zika epidemics are used today to track measles, polio, and other infectious diseases—and have proven invaluable during COVID-19. The current exemplar of this emerging capability is the globally famous COVID dashboards. There are dozens, with the most prominent being those of the World Health Organization and Johns Hopkins University
  • Contact tracing: Advanced location intelligence helps leaders detect patterns in real time, spotting anomalies, gaining insights, and quelling the spread of the disease by understanding linkages beyond cases and contacts to include the places people have visited. 
  • Protecting the most vulnerable: Smart maps that display US Census Bureau data about age and income, layered with information about senior living facilities, homeless encampments, hospitals, and clinics, have become vital. With simple spatial analytics, this layered information can create localized risk scores that are highly actionable.
Pharmacist checking medication stocks while consulting a tablet

Smart maps and dashboards are also helping with prediction and planning for how many people will need hospitalization, addressing food shortages, and enabling companies to adapt indoor workspaces for when employees return to work.

These location intelligence-based approaches allow us to move beyond personalized medicine to precision medicine, and beyond precision medicine to precision public health. 

In the end, the pandemic is telling us as much about geography as it is about health care. 

On the one hand, it reminds us that we're all in the same boat. As David Wolman put it in Wired, "the very concept of elsewhere is a fiction … Where matters—absolutely. But it's also true that we all live right here. Together." 

On the other hand, the virus is reinforcing the centrality of microlocation. The unique combinations of societal, environmental, and cultural characteristics of a given city, neighborhood, or block are decisive in determining the virus's impact on those communities. Just as important, they show us where and what to do about it.

By Estella Geraghty, a physician and the chief medical officer for Esri.