Many years ago as a pediatric resident, I walked through Ciudad Oculta, a neighborhood right on the edge of the city of Buenos Aires, to vaccinate against measles. We wore our white coats and carried the supply of vaccines in a styrofoam container. We traveled in pairs and were accompanied by a social worker. There was an epidemic of measles and we were tasked with vaccinating every child we could find. Measles can be a deadly disease, especially when coupled with malnutrition as was common in many of the children living in Ciudad Oculta. We knocked on doors or clapped our hands and were welcomed in homes all over the neighborhood.

Ciudad Oculta means hidden city, and that is exactly what it was: a neighborhood with cramped homes built out of wood and brick and tin, with makeshift and haphazard connections to the city's electrical grid and water supplies, and dirty water running down its irregular and narrow streets. There were homes and stores, a whole world, a whole "city" with thousands and thousands of inhabitants hidden just below the surface and hardly visible from the avenue nearby. Nearly thirty years later, it is still there.

As residents, we rotated for several months through city health centers located in neighborhoods like Ciudad Oculta. Each day, we saw dozens of children mostly cases of respiratory infections, diarrhea, or malnutrition, many times combined. It was moving to see how grateful the parents were to us, even though we were just residents, young and inexperienced, sometimes (often!) a little too sure of ourselves. But it was also frustrating, because we saw the same children come back day after day with problems that we really couldn't fix. We didn't use the term then, but these were the "social determinants of disease" in action.

I think it was around that time when I began to be interested in public health. But we did not call it public health, we called it primary health care and social medicine. Public health was a truly terrible class in medical school focused mostly on mind numbing regulations and an outmoded approach to tracking diseases, nothing like what we thought was really needed. I remembered this as I spoke to several Drexel medical students interested in public health a few days ago. They were wondering about a public health degree, what it could do for them, why it might be worth it.

The worlds of medicine and public health are of course closely entwined. Although often presented as opposed in their goals and focus (one focused on treating the individual patient, the other on prevention in the population) both fields need and complement each other. Many great public health leaders came from medicine, and some have had a very expansive vision of medicine. Virchow for example famously stated that "Medicine is a social science, and politics is nothing more than medicine on a large scale."

But, and this is what drew me to it, public health is so much more than medicine, it must integrate sociology, economics, politics, statistics, and so many other fields. It must grapple with complex methodologic challenge that transcend the simple clinical trial, it must consider implementation and evaluation of policies writ large. It interphases with history, ethics, and philosophy.

Sometimes people ask me if I miss seeing patients. I can't say I do, it's been such a long time. But I am grateful that I had the opportunity to experience being a doctor. I am grateful to all those patients who "patiently" listened to my advice even when I am sure they were fully aware that they knew much better than I did what was ailing them or their children. I learned so much from them, I wish I could let them know.

The things I learned and experienced as a clinician: listening, assessing, coming to a diagnosis, developing a plan, following up, are things that I do all the time every day today. The incredible opportunity a doctor is given to peek into real lives, to learn about the most intimate problems and challenges and gratifications of life, to experience not only life but also illness and death in its many forms, is unique and life changing. There is nothing else like it. Being a resident a major public pediatric hospital in the city of Buenos Aires, the largest in the country at the time, was a life experience that I think has marked me forever.

Medicine is of course not always a positive force. There is a long history of medical interventions that were useless at best, harmful at worst. From bloodletting to lobotomies to medications with major adverse effects to medical errors, the history of medicine is far from pristine. Some things that have been done in the name of medicine have been racist, sexist, and violent. Social problems are sometimes medicalized with dangerous consequences. Doctors, like all human beings, are fallible but sometimes acquire extraordinary power over the lives of others. And the medical world is far from immune from the adverse impact of powerful economic interests and lobbies.

So what did I tell those medical students? I tried to tell them about how public health had opened up and enriched my professional life in so many ways. It gave me tools and insight. It allowed me to think about health problems in completely different ways, study them using rigorous methods but also understand the nuances and complexities involved. It allowed me to engage with the world of the social sciences and policies and politics. It broadened my thinking about what "diagnoses" and what "treatments" are possible to improve health. It gave context to what I had seen as a pediatric resident in Ciudad Oculta. It gave me the certainty that we can do better to protect the health of those children, not instead of, but in addition to treating them when they are sick. But it also made me less naïve about the challenges involved.

Ana V. Diez Roux, MD, PhD, MPH
Dean and Distinguished Professor, Epidemiology, Dornsife School of Public Health