Table 1.

Binomial fitting of the province-level epidemic attack rates in the 15 provinces in Northern China.

Epidemiological year	R 2	P value	Urbanization rate turning point (%)
2010	0.61	.004	52
2011	0.51	.01	50
2012	0.76	<.001	50
2013	0.77	<.001	55
2014	0.79	<.001	55
2015	0.67	.001	61
2016	0.68	.001	57