Table 3. Legionnaires Disease Cases and Rates in the Veterans Health Administration Health Care System, 2014 to 2016.

LD Case Category	Denominator Category	No. of LD Cases/Denominator Value, No.			Rate of LD (per 100 000 Denominator Category)			P Value for Poisson Regression
		2014	2015	2016	2014	2015	2016
Total and non-VA-associated LD cases
All reported LD cases (non-VA-associated and VA-associated)a	Total enrollees in VA HCS	136/9 106 480	174/8 965 923	181/9 046 663	1.5	1.9	2.0	.04
	Enrollees who used the VA HCS in the year	136/5 843 375	174/5 927 103	181/5 995 048	2.3	2.9	3.0	.04
Non-VA-associated LD casesa	Total enrollees in VA HCS	82/9 106 480	113/8 965 923	133/9 046 663	0.90	1.26	1.47	<.001
VA-associated LD cases
LD cases with inpatient and/or LTC VA exposure (includes definite and possible HCA LD)	Unique inpatients and residents per yearb	20/397 319	15/385 662	9/394 033	5.0	3.9	2.3	<.001
	BDOC (inpatient) and resident days (LTC)c	20/6 437 769	15/6 268 381	9/5 998 084	0.31	0.24	0.15	<.001
LD cases with only outpatient VA exposure	Unique outpatients/yb	34/5 996 775	46/6 076 638	39/6 142 871	0.57	0.76	0.63	.71
	Outpatient encountersc	34/74 214 643	46/76 428 670	39/78 067 260	0.05	0.06	0.05	.78

Abbreviations: BDOC, bed days of care; HCA, health care–associated; HCS, health care system; LD, Legionnaires disease; LTC, long-term care; VA, Department of Veterans Affairs.

^aNon-VA-associated cases are patients with LD who did not have contact with a VA health care building in the 10 days prior to symptom onset. It is not possible to reliably know if there was contact with non-VA health care buildings in that period, so this category is not called “community-associated” to avoid potential assumptions of no contact with any health care settings.

^bPertains to population-level calculations.

^cPertains to exposure-level calculations.