Snow in the Time of Cholera

I know that my science colleagues are familiar with Dr. John Snow (1813-1858) and his impact on epidemiology and I think his name was bounced around a little during the pandemic times because of his work with disease vectors, but for those that have not heard of him, this post is all about the cholera outbreak in London in 1854.

But first, a couple interesting (to me) geographical tidbits. My flat in London is in Earl’s Court, which is near Chelsea, Kensington, and West Brompton. Neighborhoods (boroughs) are named based on historical people, places, land, roads, etc. and they are now usually associated with tube (London Underground) stations in the heart of those areas. So, my closest tube stations are Earl’s Court and West Brompton. Brompton is also referential to the Royal Brompton Cemetery, which I am literally looking out my bedroom window down into right this second.

It is a large cemetery and has been nice to wander around. It is interesting geographic bit number one because John Snow is buried here (and he’s not the only scientist there – more on that in a future post!). As you see from his dates, he had a relatively short life. I would imagine being in as much contact with sick people and surgery patients (he was an early anesthesiologist) as he did contributed to that. His grave marker is quite large and of the 100 marked, notable graves in the cemetery (out of the literally THOUSANDS buried there – like, over 200,000 people…), his is number 1.

The inscription reads:

To
John Snow, M.D.
Born at York
March 15th 1813
Died in London
June 16th 1858
In remembrance of 
his great labours in science
and of the excellence
of his private life
and character
this monument
(with the assent of
Mr. William Snow)
has been erected over
his grave
by his professional brethren 
and friends.

The second interesting geographic tidbit is about the location of the cholera outbreak in 1854. They call it the 1854 Soho Cholera Outbreak, which was really one of a string of cholera epidemics in the general London area at the time. Soho is primarily a shopping district now. It reminds me a bit of Times Square in New York City with its lights, moving signs, billboards on tall buildings, expensive shops, people EVERYWHERE. If you get just a smidge (technical, scientific distance measurement) off the beaten path, you can find yourself on Broadwick Street, which, in John Snow’s time, used to just be called Broad Street.

On Broadwick St., there is a pub called John Snow, and on that same corner, a monument in the shape of a traditional water pump.

And the plaque on the pump is where we will begin our story:

John Snow had an early interest in medicine and toxicology, or the study of poisons. One of the first scientific writings by Snow that we know of is a letter in response to a scientific article about the use of arsenic to preserve dead tissue. Arsenic, as we know from our love of forensic science and true crime shows, is quite poisonous to living things. The mechanism for this toxicity, from a biochemical standpoint, depends on the form of the arsenic. Without getting too much into the weeds of the details, elemental arsenic (As) is a metalloid (semi-metal) and on its own, is not harmful. When it pairs with other things, giving rise to both organic and inorganic compounds (due to its ability to act with characteristics of both metals and non-metals), then there are varying degrees of bad things it can do in the body. One of the things I learned is that it is disruptive to proteins due to its interactions with the amino acids in those proteins that contain sulfur. Arsenic is a big fan, energetically speaking, of bonding with sulfur, so it will disrupt the bonding (either chemical or attraction due to intermolecular forces), which impacts the functionality of the protein (if you have a deeper interest in this, I recommend the CDC site on its toxicity – it’s fun to me that it matches so well Snow’s description of the effects in his letter). Anyway, it was being kicked around as a potential way to preserve dead tissue back then and Dr. Snow had something to say about that:

“To the Editor of the Lancet

Sir:–As the last Number of your Journal contains an article on preserving bodies for dissection, by injecting them with a solution of arsenious acid, you will oblige me by giving publicity to my reasons for believing such a practice to be highly dangerous, as calculated to expose the dissector to breathe an atmosphere contaminated with arsenuretted hydrogen, which is, perhaps the most deadly combination of arsenic.” 

Lancet (10 November 1838): 264

You can see that the nature of Snow’s medical research was varied, but that he had an interest in the impact of substances on the body – he was an early anesthetist (a doctor who gives the patient something to dull the senses prior to a procedure) and it was definitely a simpler time when it came to testing such things on humans. They would often test first on deceased humans (more on how they got said deceased humans in a future post…), but would have to graduate to living things eventually. One of my favorite stories to tell in my classes was how they originally tested the effects of chloroform (CHCl₃) and I found some historical artifacts and reference to this in the National Museum of Scotland in Edinburgh. Without getting too far afield (I’ll do a separate post about Dr. Simpson, a contemporary of Snow, at a later time with more detail), anesthesia for surgeries and child birth were much different back in the day than we know them now.

Anyway, back to Snow. Along with his interest in toxicology and anesthesiology, he also studied disease progression and spread. He is known as the Father of Epidemiology, which is the study of just that: what populations does a disease impact? how does it transmit from one person to another? what, where, and why does it spread? Looking at the whole of his career, again, you can see how this is a fairly natural progression. As the plaque on the water pump says, Snow studied an earlier outbreak of cholera in the late 1840’s in South London (though he had come in contact with it in the 1830’s in is work with patients) and published an essay on the way he proposed it was transmitted called, “On the Mode of Communication of Cholera” (1849). In it, he hypothesized that cholera was spread in a particular neighborhood by a shared water source, which went against the common thought that it was transmitted by air (most diseases were thought to be ‘foul air’ and you could tell they were present by the smell…not entirely untrue, but not entirely true, either).

It was widely criticized in the early days and you have to remember that this is all pre-germ theory, which wasn’t widely understood or accepted until the early 1900’s. When the Soho Cholera Outbreak came about in 1854, Snow applied the same logic he had proposed in his 1849 essay and linked the people getting sick in the area to one specific water source – the pump on Broad Street. As the plaque on the modern facsimile pump says, Snow was able to convince city officials to remove the pump handle, which helped to stop the spread.

The entire pump was eventually removed for non-cholera related reasons, but the rectangle of ground where the original pump was is marked with a granite tile. The memorial pump is right next to it, but I kind of like that they acknowledged that little piece of the original pump. A practical monument for a pragmatic man.