“GENTILITY of speech is at an end — it stinks, and whoso once inhales the stink can never forget it and can count himself lucky if he lives to remember it.”

This is how the City Press described the smell emanating from the River Thames during the unusually hot summer of 1858.

With temperatures passing 40°C, the sun was gently cooking the gigantic stew of sewage, slaughterhouse waste and industrial run-off that flowed into the Thames from the struggling sewer system.

There had been complaints about the smell of the Thames for years before, but the “Great Stink” of 1858 prompted action immediately, in the form of pouring bleach into the river to ease the smell, as well as prompting the construction of over one thousand miles of sewers to cope with the expanding population of London.

Much of this sewer system remains in use today. In addition to the smell, the unsanitary conditions in Victorian London led to frequent cholera outbreaks.

It is hardly surprising that the horrible smell and presence of disease were linked in the minds of Londoners.

The leading theory of disease at the time was that breathing bad air released from decomposing matter caused illnesses such as cholera, typhoid, tuberculosis and malaria (the name of which derives from the Italian mala aria — meaning “bad air)”.

This theory is known as the miasma theory of disease after the name for the vapours that were believed to rise from decaying soil and foul water, causing disease.

This differs from the germ theory of disease that is accepted today, where micro-organisms like the bacteria Vibrio cholerae are present in water and enter the body during eating or drinking.

Miasma theory does not include the possibility that there can be human-to-human transmission of disease, which we know today can occur from contact with the bodily fluids of infected individuals.

Nonetheless, for all its flaws, miasma theory did encourage a fairly successful sanitation campaign. Sanitation reformers focused on cleaning up places that released foul smells, which through a happy accident are usually places where pathogens are likely to be present.

An early proponent of germ theory who put in a lot of effort to convert the wider medical establishment was a London anaesthetist called John Snow.

Although he suspected that cholera was transmitted from person to person, he did not know what exactly was responsible. Snow hypothesised that “epidemic diseases are propagated by special animal poisons coming from diseased persons, and causing the same diseases to others.”

During a cholera outbreak in Soho in 1854, four years before the Great Stink, Snow made a detailed map showing the houses where people had fallen ill. The cases on his map were tightly clustered around Broad Street.

Snow concluded that the water from the pump was contaminated and was making nearby people sick when they drank from it.

Snow managed to convince the local authority to remove the pump handle, preventing further infection directly from the water. He was very modest about his impact on the outbreak, admitting that it may have already been coming to an end since many people had fled the area around Broad street.

Snow’s data was a pioneering study into disease transmission. By analysing who fell ill and where they received their water from, he showed that people who drank from the Broad Street pump were far more likely to fall ill.

This kind of thinking still underpins much modern infectious disease research, comparing the outcomes (cholera or no cholera) for people with different exposures (drinking from the Broad Street pump or not).

Investigation of the Broad Street pump after the outbreak showed that the well had been dug less than a metre away from an old cesspit that had begun to leak into the well.

Unfortunately for Snow, while he had managed to convince the local council to remove the pump handle, he could not immediately convince the wider medical community of his theory.

A scientific committee into the 1854 outbreak scrutinised Snow’s theory and concluded that “After careful enquiry, we have no reason to adopt this belief.” It would take a further 10 years before William Farr, a member on the previous committee, would publicly state his support for germ theory.

Interestingly, while all of this was taking place Karl Marx was researching and writing Capital, Volume I, in his house on Dean street in Soho, only 300 metres from the Broad Street pump and even closer to Snow’s medical practice on Soho Square.

A careful reading of Marx’s work reveals the way in which he understood disease transmission and how it related to unsanitary conditions, linking this back to the material conditions of workers.

When Marx discusses the increasingly exploitative practices in the domestic lace-making industry in Nottingham, he provides a table showing how the rates of consumption (now known as tuberculosis) in young women making lace had risen from 1 in 45 in 1852 to 1 in 8 by 1861.

He links this rise in disease to the overcrowded and unsanitary conditions that the women worked in. Unfortunately, this data would not have helped John Snow vindicate his germ theory, since the overcrowding could have meant that more women were closer to a source of miasma, or that there was more person-to-person transmission of germs in cramped conditions, as Snow thought.

The Children’s Employment Commission of 1864 that is quoted by Marx to reinforce his depiction of the young women’s conditions uses the language of miasma theory.

As Marx quotes: “The crowding in these rooms and the foulness of air produced by are sometimes extreme. Added to this is injurious effect of the drains, privies and decomposing substances, and other filth usual in the purlieus of the smaller cottages.”

The power of a scientific breakthrough is very different to the political power required to wield the scientific discovery for the public good.

In the case of the Broad Street pump (a replica of which is present outside the John Snow pub in Soho), Snow was able to remove the pump handle and save lives even though his germ theory was not broadly accepted.

In the present day, the germ theory of disease is universally accepted, yet thousands of people continue to die each year from easily treatable illnesses.