[Choi Jun-young's Urban Pilgrimage] Epidemics and Metropolises

Humanity's struggle with epidemics began alongside the growth of large cities
Introduction of sewage systems and asphalt roads maintained urban cleanliness
In the 21st century, virus-originated epidemics threaten cities
Advancements in transportation spread viruses across borders worldwide

Choi Jun-young, Senior Advisor at Yulchon LLC

How did cities come into existence? For a long time, people believed that surplus agricultural products resulting from the agricultural revolution that began after the Neolithic era made the birth of cities possible. This is because cities, which do not produce food essential for human survival, require food supplies from outside to survive. However, archaeological discoveries have confirmed that some cities appeared even before the advent of agriculture, leading to the understanding that cities emerged due to various factors such as defense, trade, and redistribution.

Regardless of the cause of their emergence, once cities appeared, they grew on their own. Just as flat glass cannot concentrate sunlight but glass curved in one direction forms a lens that can gather sunlight to start a fire, people gathered in the space called a city create developments and changes in directions that were previously hard to imagine. The various activities and services provided in the urban space can only emerge and be sustained through the interactions of the large population within the city. The differences in services available between a city of one million people and a city of ten million are created by the scale of the city.

The novelty and uniqueness generated by cities attract people. In the past, in an agriculture-centered society, cities that existed separately from agriculture were regarded as belonging to another world. Hence, the phrase "the air of the city is free" emerged in medieval Europe. Medieval Europe was a self-sufficient feudal era based on agricultural manors, but since each region had goods it needed, cities emerged as centers of trade connecting these regions. Urban life required not only simple diligence but also quick wit, situational judgment, and decision-making. Thus, cities increased tension, accelerated exchange, and continuously transformed people's lives.

In advanced countries, the urbanization rate is high, while in developing countries it is low. Conversely, countries with low urbanization rates can still be seen as having high development potential. Imagine a society where everyone is engaged in agriculture. In such a place, as the population increases, the land available per person decreases. When farming on small plots of land, it is difficult to expect technological innovation or development. As urbanization progresses and people leave rural areas, the farming area per person gradually expands, creating opportunities for the application of technological advancements such as mechanization and automation. People who move from rural areas to cities are more likely to engage in fields that produce higher added value, which results in increasing the overall added value of the country. Ultimately, the growth and expansion of cities have been the driving force of development and the source from which innovation and novelty emerge.

However, the growth of cities, especially large cities with populations exceeding one million, did not occur easily. City growth, conversely, brought congestion. While complexity has a positive meaning of various relationships, congestion implies disorder and confusion that hinder the formation of relationships. Cities grow until the benefits of complexity outweigh the costs caused by congestion; beyond that point, they stagnate or decline.

Additionally, factors limiting city growth included disease and public health. Infectious diseases caused by bacteria and viruses require a population above a certain threshold. If the population is too small or spread out too widely, infectious diseases do not spread and eventually disappear. As humans began to create and live in the space called "city," infectious diseases started to form in earnest and have evolved alongside humanity. Many infectious diseases originate from animals and spread to humans, and the more people concentrated in one place, the faster they spread. In times lacking scientific knowledge of diseases and concepts of hygiene, the only measure against outbreaks was to abandon the city and move to sparsely populated rural areas. The population and size of cities have repeatedly grown and shrunk through such processes.

The introduction of water supply and sewage systems, along with road paving, which began in earnest in the late 19th century, freed cities from past constraints and enabled their growth. Previously, such developments would have consumed unimaginable costs, but the wealth gained from the Industrial Revolution made these changes possible. The advent of asphalt and cement-paved roads, often seen as symbols of barrenness, allowed cities to maintain cleanliness with fewer people. The spread of water supply and sewage systems blocked the causes of waterborne diseases that frequently occurred, and the development of antibiotics and medical technologies, which began to be widely distributed in the mid-20th century, became the driving force that allowed cities to grow freely, breaking free from past shackles. It seemed as if cities had achieved a complete victory in the battle against disease.

However, in the 21st century, infectious diseases, especially those originating from viruses, are once again threatening cities. The population increase due to urban growth and expansion required larger areas, which increased contact with wild animals. As natural ecosystems were damaged, bacteria and viruses living with animals in those environments came into close contact with humans. Once bacteria and viruses infiltrated cities, they could easily spread in various forms of disease. Furthermore, with the expansion of transportation speed and range through high-speed trains and airplanes, infectious diseases no longer remained confined to specific regions but began to spread worldwide in a short time. In the 21st century, we have witnessed SARS, MERS, and the recent novel coronavirus all spreading rapidly beyond specific regions or countries to the entire world.

Can current and future cities survive the counterattack of infectious diseases? Until recently, we thought there was no need to worry about such events, but witnessing successive outbreaks and the resulting chaos has shaken this confidence. Since the 21st century, the polarization trend between a few shining large cities worldwide and the rest of the regions becoming desolate like deserts has intensified. Although this trend seemed inevitable, the repeated occurrence of large-scale infectious diseases raises many questions about the future of cities.