“Hindsight is 20-20. If we knew everything we knew now, probably there would have been more intervention earlier, but we didn’t have that crystal ball at the time,” said the CDC’s Butler. “Now we know people can be infectious before the onset of symptoms.”

3. Perfect Environment
With the virus’s easy transmission, New York’s shared spaces were a perfect vector to bring the infection from one family to another.

Subways and buses, concert halls, elevators, offices, crowded bars, apartment towers — while other U.S. urban areas have natural social distancing built into their structure through the prevalence of cars and less-dense buildings, New York is defined by crowding.

“In a place that doesn’t have a car culture, that relies on mass transit, there are more opportunities for it to get into households and move around,” said Columbia’s Shaman.

A May 8 CDC report drew a similar conclusion. The agency noted that the four most dense counties in America are New York City boroughs. Combine that with public transit, three major transportation hubs and 1.6 million daily commuters into Manhattan, and it’s a perfect human mixing bowl.

In his emailed statement, de Blasio said the city’s mass transit system had been a major factor.

“New York’s subway system stands alone,” de Blasio said. “New York City is different than Los Angeles and Seattle and pretty much everywhere else for how heavily the population relies on travel by subway. The subway has been a lifeline for our essential workers, but we also now know that prolonged, close contact during a commute may have been an issue long before we knew the virus was even in the city.”

4. Slow to Close
For all of New York City’s risk, its leaders moved late on shutting down the city.

Cuomo and de Blasio — who have had a long-running, often public feud — disagreed for days over how and when to act. The city closed the schools on March 15. Two days later, de Blasio raised the possibility of a stay-at-home order. Cuomo disagreed, saying it was the state’s decision and that he had “no interest whatsoever or plan whatsoever to contain New York City.” On March 20, he announced that the state would shut all non-essential businesses, and told people to stay home.

Butler said those decisions are difficult at the early stages of an outbreak. “When we evacuate a city for a hurricane, we don’t do it based on when there’s something out off the coast of Africa,” he said. “We do it when there’s much clearer visibility of when it’s going to happen. It’s much harder with an infectious disease, particularly a brand new one.”