Open this photo in gallery Pariser Platz in Berlin sits nearly empty on March 19, 2020. Maja Hitij/Getty Images

I have seen things this week that I could not have imagined: This city’s great public squares and boulevards, Alexanderplatz and Unter den Linden, and the Gendarmenmarkt utterly devoid of other humans, their still-visible shrapnel scars a reminder of the only other time they’ve been so vacant. Great cathedrals without another soul in them. Major streets emptied of traffic.

The people of this grubby, riotous metropolis have been scared and coerced into hiding. It’s a fear only big cities fully know and a form of protection only big cities fully offer.

When a pandemic comes, cities scare the hell out of people. The crush and bustle of the sidewalks and subways feels like a big petri dish. One instinct is to run. The literature of viral apocalypse, including recent masterpieces such as Robert Harris’s The Second Sleep and Emily St. John Mandel’s Station Eleven, starts with masses fleeing to the countryside. This choice rarely turns out well.

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That’s the paradox of the megalopolis. Its population density means it’s the place where viruses often begin and that epidemics, if undetected, can explode fast there. New York is about to become a major focal point of infection and mortality, and London is not looking too good, either, because they didn’t close their crowded drinking places earlier.

But the biggest cities are also the safest places in the world.

Only they have the infrastructure, staff and organization to really quash an outbreak – Taipei and Tokyo, both more dense than New York, were able to flatten their virus-spread curves almost instantly using the unavoidable communications, visible deterrence and bureaucracies that only a tight-packed urban centre can muster. If you’ve spent any time in a small town, you’ll know how hard it is to keep people inside or away from each other.

Open this photo in gallery Pigeons had Las Ramblas to themselves in Barcelona on March 19, 2020. Maria Contreras Coll/The New York Times News Service

And only huge cities have the resources and the reserve armies of medical talent to tool their health-care systems up to pandemic-level capacity in time to save lives. New York, because it’s able to build and staff huge convention-centre hospitals in short order, will have a lower mortality rate than the smaller, more elderly towns and cities that will be hit next.

When the virus does arrive, it is often the small places that are truly terrifying. Nembro, Italy, population 11,500, saw its small hospital overwhelmed in days; 120 people died in three weeks, more than the town usually sees in a year, as dozens of people were essentially left to die; nearby Bergamo has become infamous for its gymnasium-sized triage area, where most of the dying are denied access to the handful of ventilators.

In the United States, the places with the most unmanageable outbreaks so far have been New Rochelle, N.Y., and Kirkland, Wash. – suburbs without big-city hospital resources. Modern travel and prosperity mean the disease will soon hit countless towns with one-emergency-bed hospitals and hundreds of residents older than 80. Their only hope is to get shipped to a larger city.

Rome lay empty on Monday as a government-ordered shutdown to contain the spread of the coronavirus, under which all non-essential movements are banned and shops and parks are closed, continues. The Associated Press

Still, we have an atavistic, deep-set fear of big cities as pits of disease. For thousands of years, that is what they were – until their very scale, and the things they contain, flipped the formula upside down.

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Cities were, until the 19th century, “population sumps,” in the words of the late Canadian historian William H. McNeill, that attracted thousands of immigrants every year and promptly killed them with epidemic diseases. London required 6,000 immigrants a year in the 1700s just to maintain its population of 650,000 because disease deaths greatly outnumbered births.

Then two things happened. First, the tight-knit populations of cities, and their connections to other cities, meant that the urban world became a homogenous human pool of immunity. The practice of inoculation saw its first widespread Western practice in the English countryside at the end of the 18th century to fight smallpox – by that point, Londoners didn’t need it because their immunity had transformed it into a fairly harmless childhood disease. In 1790, London baptisms outnumbered deaths for the first time and, from then on, cities became safer than towns.

Open this photo in gallery London lays quiet during rush hour on March 18. Andrew Testa/The New York Times News Service

Second, the middle of the 19th century saw a revolution in digging fresh-water pipes and drains, and building hospitals and filtration plants that launched an urban hygiene revolution – one that only the largest cities could contemplate. By the end of that century, Dr. McNeill wrote in Plagues and Peoples, “for the first time since cities had come into existence almost five thousand years previously, the world’s urban populations became capable of maintaining themselves and even increasing."

Big cities changed in a few decades from sump-pits of disease into rare islands of safety. They still scare us, but they remain our best hope for survival.

Doug Saunders, The Globe and Mail’s international affairs columnist, is currently a Richard von Weizsaecker Fellow of the Robert Bosch Academy in Berlin.