Table 2.

Assessment of temporal trends of anthrax events using Poisson mixed-effects regression model with calendar month as fixed effect across years

Variable	Variable category	Coefficient	95% confidence interval	P value
Month	January	Reference
	February	1.04	[0.70, 1.63]	0.43
	March	1.11	[0.77, 1.65]	0.55
	April	1.05	[0.72, 1.55]	0.76
	May	1.09	[0.76, 1.62]	0.62
	June	1.05	[0.72, 1.55]	0.76
	July	1.13	[0.79, 1.67]	0.49
	August	0.61	[0.39, 0.97]	0.03
	September	0.88	[0.58, 1.31]	0.53
	October	1.32	[0.50, 1.15]	0.19
	November	1.11	[0.77, 1.65]	0.55
	December	0.66	[1.65, 1.01]	0.06
Random effects County identification:	–	Standard deviation =1.57		–

Likelihood ratio test versus Poisson regression chibar2(01) = 1441.2; Prob> = chibar2 = 0.0000