Originally Posted by
iceman
re: CA vs. NY. I just spent some time trying to find the Times article I read a few days ago without success but the point of the article was that the source of the New York outbreak has been pretty clearly nailed down as being Europe. The source of the CA infection is known to be China. There is far more direct travel between China and California than there is between China and NY, 8 times more IIRC. Because of the huge amount of travel to CA from China, the idea is that the disease got to CA well before it got to NY, brought there by travelers from Europe who got it from China directly or indirectly at some earlier point.
Essentially (goes the theory) it all goes back to transmissibility and herd immunity and the date that the outbreak actually began. The date when the disease arose is unknown. China has pushed it back several times (possibly as far as November is the current thought, but it could even be earlier). It circulated for some time before it was discovered. Prior to that discovery CV cases were thought to be flu cases and didn't raise any particular alarm.
Because there is so much travel between China and CA (again, in the theory) the disease was introduced to CA very early and spread rather quietly. People were getting sick, but nobody had ever heard of CV at that point, so there was no particular alarm. Because of the transmissibility of the disease, and the fact that nobody even knew it existed. CA was able to develop a level of herd immunity that New York did not have on the same dates.
Add in the differences in population age and overall health, population density and the way people live (as Benny pointed out, cars v. subways would be one such difference) and voila. Obviously randomized sampling is needed to establish infection rates but the belief is/is theorized to be that such testing would show that a much higher percentage of Californians have had the disease than of New Yorkers. As the disease spreads everywhere it may not be possible to prove this theory in the future, in fact it may be too late now.