Despite John Snow's discovery that cholera was transmitted via contaminated water many older physicians still advocated the atmospheric malaise/predisposing condition theory to explain the disease’s source. And even though Snow understood that human excrement had something to do with the spread of the disease, the cholera vibrio-- the specific bacteria that caused cholera-- would not be discovered until 1883.

Resistance to Snow's work was part of a larger hesitancy among physicians to accept "germ theory" — the belief that most diseases were caused by organic entities rather than chemical reactions or divine punishments. Those who saw Snow's work as proof that cholera was contagious believed that only organic entities — germs — possessed the power to reproduce themselves. The findings of the French chemist Louis Pasteur, which undermined the long-held notion that living organisms could spontaneously generate from nonliving matter had been gaining adherents since the late 1850s and implicitly supported Snow’s work. By the mid-1860s a great divide had emerged among physicians around the question of contagion and causation of disease. Mid-nineteenth century science was increasingly being defined by an empirical approach that, while not eliminating entirely the socially-constructed symbolisms that many attached to diseases, did allow for more scientific and effective responses to outbreaks.

As with earlier epidemics, lay persons in 1866 New York City needed no prodding to conclude that cholera was contagious. New Yorkers in general may have not had the language or knowledge to participate in scientific debates, but common sense revealed that cholera moved from place to place. Despite the continued presence of those who clung to the older view of disease, the increased acceptance of Snow's work combined in 1866 with the desire of city leaders to more aggressively attack the city's problems. Faithfully cleaning the streets in the face of an epidemic outbreak was a significant step beyond the inactivity of previous years. But in the mid-1860s, New York City would do more than sweep the streets.