Table 2.

Summary of monthly contributions of cases during two time periods

	1993–2002	2003–2015
Month	Mean (s.d.)	Mean (s.d.)	δ	p-value*
Jan	4.937 (1.493)	4.158 (0.463)	−0.779	0.089
Feb	6.117 (1.330)	3.938 (0.528)	−2.179	<0.001*
Mar	6.266 (0.770)	4.310 (0.858)	−1.956	<0.001*
Apr	6.323 (1.997)	3.911 (0.688)	−2.411	0.001*
May	6.155 (1.632)	5.549 (1.394)	−0.606	0.348
Jun	7.326 (1.307)	9.588 (3.005)	2.262	0.038*
July	9.167 (1.865)	12.903 (2.321)	3.736	<0.001*
Aug	10.124 (2.542)	13.635 (2.258)	3.512	0.002*
Sept	9.798 (2.094)	12.542 (2.204)	2.745	0.006*
Oct	11.077 (2.123)	11.312 (2.643)	0.235	0.821
Nov	8.973 (3.110)	8.085 (1.279)	−0.888	0.360
Dec	13.737 (2.142)	10.068 (1.840)	−3.669	<0.001*

*Significant (by analysis of variance).