[illvm]

There's the theory of Vitamin-D deficiency. It would make some sense given NYC's climate and time of year. In LA, people likely are exposed to the sun year round. It would be interesting to see if other respiratory illnesses exhibit a similar pattern between these two cities, as I understand Vitamin-D levels have an affect those as well.

But also, NYC is considerably more dense, so diseases spread far more rapidly. Especially so considering heavy public transit use versus, what I would say is, extreme overuse of personal vehicles.