It is one of the most diverse. And the people were being funnelled into a large crowded city with heavy reliance on mass transit.
Why coronavirus pandemic hit New York City so hard
A Financial Times analysis of hard-hit places has only Bergamo, Italy, and Guayas, Ecuador, running ahead of New York in percentage of excess deaths — not Madrid, London or Ile-de-France.
The epidemic started early in New York. According to one model, the city had its first 10 cases at the end of January or by the middle of February.
By the time it had its first confirmed case on March 1, there may have been as many as 10,000 undetected cases.
The city was getting seeded constantly from abroad. A study published by medrxiv.org concluded that “introductions from Europe account for the majority of cases found in NYC in the first weeks of March 2020.” It found “isolates from Italy, Finland, Spain, France, the U.K. and other European countries from late February.”
Then, people coming from or through New York spread the disease elsewhere in the United States. A New York Times analysis found that the number of cases around the country correlated with how many travelers arrived from New York in early March.
New York’s connection to the world, especially Europe, its density and its mass transit system all made it a potent vector.