"Density alone doesn’t seem to account for the scale of the differential between New York’s fatality rates and those of other cities."

"New York has twice the density of London but three times the deaths, and the differential is even higher [comparing NYC to] cities such as San Francisco and Los Angeles. Deaths have occurred disproportionately in poorer areas, where the incidence of long untreated morbidities such as heart disease and diabetes have contributed significantly. But the same is true in all other cities. The high dependence on mass transit also seems to be a factor. In other major cities, car commutes are much more common. As Joel Kotkin, a scholar of cities at Chapman University in California, says, it may be the lethal convergence of all three factors. 'If you put together density, levels of poverty and reliance on a mass-transit system, you have a hat trick,' he told me.… But even that may not explain the extent of New York’s unique catastrophe. Around the world, the highest death rates have occurred where hospital systems were overwhelmed in the early stages of the crisis. This is especially true in northern Italy. Anecdotally, at least, it seems that the same happened in New York: Large numbers of sick people never got to hospitals, arrived too late or, in the impossible circumstances that medical personnel were confronted with, were given ineffective treatment.… It will be a while before we get a proper understanding of what went so tragically wrong...."

From "The Covid-19 Catastrophe Unfolding in New York Is Unique" (Wall Street Journal), quoted at my son John's Facebook page.

John writes:

I'm not sure this is a logical argument:

"Density alone doesn’t seem to account for the scale of the differential between New York’s fatality rates and those of other cities. New York has twice the density of London but three times the deaths, and the differential is even higher for cities such as San Francisco and Los Angeles."

Doesn't that assume there's a linear relationship between density and infection rates, and isn't that not necessarily the case?

My question is about the comparison of New York to northern Italy, where hospitals were overrun. Were NY hospitals overrun? I thought they weren't.  I think the 3 factors named — density, reliance on mass-transit, and the bad health conditions represented by the term "poverty" — are enough to explain what happened. These things are interactive. Shouldn't we talk about Bayes theorem?