Late last year, what is thought to be a bat-associated coronavirus infected humans in Wuhan, a city of 11 million in China, possibly after a stopover in illegally traded pangolins—setting off a global pandemic. This kind of thing has happened before—with AIDS, SARS, and MERS, for example. Much remains unknown about the biology of COVID-19, which is alarmingly communicable by people with few or no symptoms. But an epidemic is only part biology. It is also driven by cultural factors, and urbanization is a crucial aspect. As sites of large gatherings and dense living conditions, cities offer the perfect settings for the spread of infection, yet their role seems to have often gone unremarked in discussions of the pandemic.

Cities are home to more than half of the world’s human population, and account for more than 70 percent of global GDP. They can generate an oversize impact on the environment, but also opportunities for enhanced well-being through access to healthcare, education, and social connections. At the same time, deep inequalities and poverty mark cities in both developed and developing countries, bringing anger and resentment close to the surface. Especially relevant in the current pandemic, poor people the world over—including the 1.2 billion people living in slums and over 70 million forcibly displaced people and refugees—lack safe, provisioned, low-density environments for sheltering in place.

Other recent disease outbreaks have also thrived in urban settings. Zika, a mosquito-spread viral disease originally isolated in Uganda, spread explosively in two Brazilian cities in 2015, ultimately affecting an estimated 1.5 million people and causing microcephaly in thousands of newborns. High human density and the presence of invasive species of mosquitos that arrived previously and were not considered a major threat but that can transmit the disease, unlike the native ones, allowed the disease to spread rapidly once it arrived in American cities, harming thousands.

After spreading in China, COVID-19 quickly emerged in urban centers around the world. Genetic studies suggest that the cases reported in Washington state in late February had their source in China, although community spread was apparently already occurring in California at that point. By then the disease had also reached New York – via Europe. Soon it spread to other urban centers, with cases traced to both internal movement and new arrivals from around the world. U.S. residents were reminded that markets in faraway cities and students returning from study abroad can wallop health, cripple economies, and hurt national security.

The connectivity within and among cities is key to “superspreading events” that boost the speed of the virus’s infection rate. If COVID-19 had hit Wuhan a century ago, before the city became a hub for thousands of daily travelers heading near and far by train, bus, and air, COVID-19 would not have had such a rapid, global impact. Where effective human mobility control measures were put in place, the spread was mitigated. In contrast, a mass celebration in Milan, after Italian Atalanta beat Spanish Valencia in the UEFA Champions League, contributed to the explosive spread of COVID-19 following the return of Italian and Spanish fans to their home cities. Despite relatively little testing, the first US case in a rural county was confirmed in late February. Today, the disease has been confirmed in nearly every county in the United States and virtually every nation on the planet. John Donne was mostly correct: no man is an island – especially if s/he lives in or near a city.

During the 2014 Ebola outbreak in West Africa, the United States devoted hundreds of millions of dollars to aid the fight. Billions of dollars are being allocated to COVID-19 and its near-future impacts, both domestically and globally. What of the long term? AIDS gave us Safe Sex domestically and the President’s Emergency Plan For AIDS Relief (PEPFAR) abroad. What will COVID-19 teach us? Will people move away from big cities? The answers may depend on whether this is the “once-a-century threat” that a recent Wall Street Journal editorial called it, or recurring, as the World Economic Forum expects. A rare event might soon be disregarded, but cyclical pandemics will surely lead to long-lasting actions. We offer four policy recommendations for consideration:

1. Prevention rather than response. Expand studies to understand the biology and ecology of COVID-19 and other viruses and natural phenomena with the potential to infect humans. Early measures such as disease surveillance needs to begin before a disease crosses over. The more we know in advance, the better we become at quickly developing tests, vaccines, and other remedies. The earlier we act, the less the impact.
2. Invest in cities as critical drivers of sustainable and inclusive development. Both challenges and opportunities abound in urban settings, yet governments and aid organizations have not been sufficiently engaged. With projections that 68 percent of the world’s population will be living in urban areas by 2050, a sustainable planet will depend on how cities grow, function and respond to stress. Better technology and urban policies can improve quality of life, reduce congestion, and decrease greenhouse gas emissions at home and in countries where U.S. foreign assistance is provided. The national security advantages of targeted urban investment can be broad and multilayered.
3. Address Global Wildlife Trade. About 70 percent of novel diseases start in animals, often via the illegal wildlife trade. Eliminating wildlife trafficking is a bipartisan priority for the United States. COVID-19 is a timely call to double down on efforts to enforce and expand existing international agreements on this topic.
4. Adopt a “one health” approach. More comprehensively, policy solutions must acknowledge that human health is tightly linked with that of other species and the environment. Not all novel diseases are coronaviruses. Many others are vector-borne, transmitted via mosquitos or ticks, many of them invasive. It is time to take invasive species, which cost the United States over 120 billion dollars every year, and other environmental challenges more seriously.

Whether COVID-19 does more damage in dense cities or in rural areas that have fewer medical facilities, less financial resilience, and less stringent social distancing remains to be seen. So far, the majority of cases and fatalities in this first wave of COVID-19 have been in cities. We must learn from this tragedy. There is little time to waste.

Disclaimer: The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of any agency of the U.S. Government. Assumptions made within the analysis are not reflection of the position of any U.S. Government entity.