It appears COVID may have been spreading in China as early as last August:
https://edition.cnn.com/2020/06/08/heal ... jem10point
If that's true, then it had to be in Europe, NY, and all international travel hubs by last fall at the latest. It occurs to me that last fall was a particularly bad flu season, attributed to the vaccine being a wrong guess as to the dominant type of flu. I bet it was actually a mix of COVID and flu.
It looks like NYC cases have continued to decrease (see
https://www1.nyc.gov/site/doh/covid/covid-19-data.page) despite the combination of Memorial Day, 2 weeks of mass protests/riots, yesterday's reopening which was preceded by many businesses stepping up their game without the state's blessing, and a general increase in the numbers of people who are just over it and are heading outside to enjoy the early summer weather.
I'm not surprised that the disease will continue to spread slowly, finding pockets of vulnerable populations here and there - and it has nothing to do with the reopenings. I bet Arizona's problem is the large number of Hispanic migrants. They are uniquely vulnerable to COVID, along with black populations, for reasons that can be guessed at but aren't really known. They may also not be doing enough to protect their nursing homes. You might want to see if a breakdown by race/ethnicity/age of hospitalized cases is available. Also make sure it's hospital cases as that's the only reliable measure given the effect of increased testing.