Cholera tore through New York City in the summer of 1832, leaving its victims with sunken eyes, blue skin, severe diarrhea, nausea and vomiting. It had swept from its origin in Asia and then made its way across Europe before arriving at New York’s shores. It only took a matter of weeks for cholera to claim the lives of more than 3,500 of the city’s 250,000 citizens (at a similar death rate, the fatalities in New York City would top 118,000 in 2020).

When cholera returned for a second round in 1849, the death toll exceeded 5,000 in the city. Throughout the 1800s, recurring cholera outbreaks left an indelible mark not only in terms of death counts but in spurring urban design elements such as wide boulevards and parks that transformed New York and other major cities into the iconic metropolises we know today.

Nineteenth-century cities were crowded, filthy places that provided the perfect breeding ground for diseases such as cholera. While garbage, animal manure and human waste flowed freely into drinking water sources, it was the pungent cocktail of odors they produced that many medical professionals blamed for spreading disease.

Public health officials adhered to an idea dating back to the Middle Ages that infectious diseases were primarily caused by noxious vapors known as “miasma” emitted from rotting organic matter. Miasma theory proponents advocated for better ventilation, drainage and sanitary practices to rid cities of foul-smelling, malevolent air. City leaders in New York, for instance, responded to cholera outbreaks by banishing 20,000 pigs from the heart of the city and constructing a 41-mile aqueduct system that delivered clean drinking water from north of the city.

“The fear of miasma probably made the most significant impact on the built environment in the wake of cholera and yellow fever epidemics,” says Sara Jensen Carr, an assistant professor of architecture, urbanism and landscape at Northeastern University. “Chiefly, it drove massive infrastructural initiatives in emerging cities, such as the installation of underground wastewater systems. That infrastructure in turn often meant the streets above them were made straighter and wider, as well as paved over so they could more easily be washed down at the end of the day so piles of waste would not emit miasmic gases. Marshy areas of cities were also filled in, which allowed for the expansion of industry and housing as well.”

Carr, author of the forthcoming book The Topography of Wellness: Health and the American Urban Landscape, says that while the familiar city street grid dates back to Ancient Rome, it grew in popularity because of the infrastructure improvements implemented in reaction to pandemics. Long, straight thoroughfares eliminated the pooling of fetid water in road curves and allowed for the installation of long drinking water and sewer pipes.

Another miasma theory devotee, landscape architect Frederick Law Olmsted, advocated for the healing powers of parks, which he believed could act like urban lungs as “outlets for foul air and inlets for pure air.”

“His writing often references the importance of large open spaces to allow people to access fresh air and sunlight, and discusses how air could be ‘disinfected’ by sun and foliage,” Carr says. Planning for Central Park, which would be designed by Olmsted and Calvert Vaux, began in the immediate aftermath of New York’s second cholera outbreak. Thanks to the success of that project, Olmsted, whose first child had died of cholera, went on to design more than 100 public parks and recreation grounds including those in Boston, Buffalo, Chicago and Detroit.

As cholera roared through London in 1854 and took the lives of approximately 10,000 of its residents, British physician John Snow mapped instances of the disease in one neighborhood and found a connection not to contaminated air, but to a public well contaminated by leaking sewage. That same year, Italian anatomist Filippo Pacini, isolated the bacterium that caused cholera, but it would be decades before the discovery was widely accepted.

In the interim, raw sewage continued to overflow into the River Thames, and in the summer of 1858 it caused the “Great Stink,” an odor so repugnant it forced the closure of the Houses of Parliament and the construction of a modern sewer system that transported the city’s waste far enough away from London that the river’s tides took it out to sea. In addition, the muddy shorelines of the Thames were narrowed and replaced with embankments with riverside roads and gardens.

Across the English Channel, Emperor Napoleon III came to power in France in 1848 amid a cholera outbreak that took the lives of approximately 19,000 Parisians. An admirer of the parks and garden squares of London, the nephew of Napoleon Bonaparte sought to remake Paris in the wake of the pandemic. “Let us open new streets, make the working class quarters, which lack air and light, more healthy, and let the beneficial sunlight reach everywhere within our walls,” he declared.

Under the direction of Baron Georges-Eugène Haussmann, French authorities tore down 12,000 buildings, built tree-lined boulevards and parks, erected fountains and installed an elaborate sewage system that transformed Paris into the modern-day “City of Light.”

“Haussmann’s plans were in part designed to bring fresh air and light into the dense urban grid, and were cited as such when inspiring the plans of Chicago and Washington, D.C.,” Carr says, “but it should also be noted that Haussmann’s long boulevards were also a convenient way to eliminate blighted housing, facilitate surveillance and deploy military quickly to all corners of the city.”