How has New York become so rapidly an epicenter of Covid-19? With more than 35,000 cases in a population of 19.5 million people, it's now more seriously affected by it than Italy (or it's testing more people, I don't know what's going on there now).
I don't know, although I could site a lot of possible factors:
Extreme density of population-hi-rises or single and 2 family homes attached on both sides
A governor, who although he's doing a good job now, was one of those who said it was racist to block travel from China and other countries, that in a city serviced by three international airports.
A mayor in New York City, the worst offender, who downplayed the risk for the same reason, and he and other city politicians encouraged people to go to the multiple Chinese Lunar New Year festivities to show "solidarity".
(The mayor of New Orleans let the Mardis Gras festivities go on, and now Louisiana is catching up as a hot spot. Florida will be next, because they didn't close the beaches, close down the sale of alcohol, and disperse the idiot "Spring Breakers" partying all over. The over 65s are a huge percentage of the Florida population, so I predict a bloodbath, much as it pains me to think about it.)
The same mayor delayed closing the schools out of concern that the inner city children wouldn't get their free meals. Laudable, but there were ways around it, as Governor Cuomo showed by handing him a plan for how they could get them.
No attempt by said mayor to stop children and teenagers from huddling together on playgrounds playing basketball etc. Again, the governor had to demand a plan to control it.
Finally, a huge percentage of New Yorkers, of all walks of life, go to work, shop, etc. by mass transit: buses and subways. They're open 24/7. I doubt most people, especially teen-agers, treat the turnstiles and bannisters like agents of the devil the way I always have. They're bound to be crawling with the virus. Yet, should they close them and really pen them in? I don't know. All I know is that I'm glad we moved out to the suburbs.
The percentage of people in New York who can work from home (i.e. tech people etc.) is quite small compared to someplace like Washington State. There, even before the government issued stay at home orders, the big tech companies, who employ a big share of the population, closed down and had people work from home. There were also cancellations of mass gatherings.
People made fun of them for being "snowflakes", but it might have had a big impact.
Also, west coast cities are very spread out in terms of area, whereas New York had to build up or pack people in in different ways.
Lastly, everybody has to have a car; no people using mass transit 24/7.
In case you've never been to Queens:
Flushing:very heavily East Asian now
Ridgewood: a nice middle class area, still mostly German-American
Astoria: once Italian and Greek, now increasingly a bedroom community for upper class commuters to Manhattan, although the oldtimers still hold on.
This is the New York foreigners don't see. All these people take public transport, they're all in close proximity to each other in food stores, dry cleaners, churches etc.
It's very different from Seattle or San Francisco. I like it better, but it's a perfect petri dish for this kind of outbreak. I would think Brazilian cities would be as well?