From the London Cholera Outbreak to the Opioid Crisis: Ignoring the Data

How challenging it can be to change entrenched beliefs

( By clicking the audio above you will be able to hear me reading this short essay, despite having a small cold:-))

In 1854, London was under siege by a terrible killer disease. The cholera epidemic that swept through the Soho district seemed to be everywhere, striking down rich and poor alike, and people had little idea why. The leading theory of the time was that the disease was carried through the air, the dreaded "miasma," a cloud of poisonous vapor said to rise from the city’s filth. This idea was comfortable because it was easy: sickness was a matter of bad air, and staying healthy meant avoiding bad smells.

John Snow, a physician and early pioneer in anaesthesiology, thought differently. He suspected the problem wasn't in the air, but in the water. Unlike most, Snow wanted proof. He collected data the hard way: by going door-to-door, noting who was sick, who had died, and where they had drawn their water. Snow was trying to do something that seemed almost too modern for his time, he was mapping an outbreak, trying to draw a connection between data points in a way that, today, is commonplace in public health.

His investigation led him to the Broad Street pump. Almost everyone who had fallen ill had drunk from that water source. Snow convinced local officials to remove the pump handle, cutting off access. Soon after, the outbreak began to subside.

Despite this success, Snow's conclusions were not immediately accepted. Many of his contemporaries were still firmly attached to the miasma theory and saw the decline in cholera cases as coincidental. Snow's idea that cholera was waterborne was considered radical and faced significant skepticism from the medical community. It wasn't until much later, after additional studies and the work of scientists like Robert Koch, that Snow's theory gained broader acceptance. This resistance to new ideas shows how challenging it can be to change entrenched beliefs, even in the face of clear evidence. This was one of the earliest examples of how data could overturn a long-held belief. It wasn't enough to say that miasma was wrong; Snow had to show, with evidence, that a different cause made sense. The pump handle was his proof, a simple action that shifted public perception.

Snow’s breakthrough offers a timeless lesson: real change doesn't come from presenting an alternative idea alone. It comes from collecting evidence and then acting on it. It demands not just data but the courage to question established norms. The power of Snow’s work wasn't just in his insight about water, it was in his willingness to confront and dismantle a comforting, dominant narrative.

This lesson is especially relevant today. Many fields still cling to outdated or comfortable ideas, even when evidence points elsewhere. Consider the opioid crisis in the healthcare industry, where evidence of harm was ignored for years despite mounting data. For instance, early studies showed that opioids were highly addictive, and internal documents from pharmaceutical companies like Purdue Pharma revealed knowledge of the risks. Much like Snow, those advocating for change had to push against established norms and entrenched beliefs about the safety of prescribed opioids. Individuals like Dr. Andrew Kolodny, co-director of Opioid Policy Research at Brandeis University, and organizations such as Physicians for Responsible Opioid Prescribing (PROP) played key roles in challenging pharmaceutical companies and pushing for awareness of the addiction risks associated with opioid medications. However, for too long, warnings from these healthcare professionals about rising addiction rates were downplayed, leading to widespread misuse and devastating consequences. Between 1999 and 2020, it is thought that prescription and illicit opioids were responsible for 500,000 deaths. Much like Snow, those advocating for change had to push against established norms and entrenched beliefs about the safety of prescribed opioids. To make progress, we need to adopt Snow's method: challenge our assumptions, gather the evidence, and be ready to act on what it tells us, even if it forces us to let go of old comforts.

Snow didn't have a laboratory, a government grant, or widespread public support. He had data, a theory, and the determination to test it. His work helped build the foundation of epidemiology and taught us that knowledge alone isn’t enough; we need action, and we need a culture willing to embrace change.

Today, as we face challenges that range from public health to AI technology, social media addiction, and other societal challenges, the story of John Snow reminds us that breakthroughs start with a willingness to question what everyone else accepts. It reminds us that data is only as powerful as our willingness to follow where it leads, even if that means pulling the handle off the pump.

Stay curious

Dr Colin W.P. Lewis

(Thank you Mateusz for suggesting I read widely on John Snow)