Legionnaires’ disease case-finding algorithm, attack rates, and risk factors during a residential outbreak among older adults: an environmental and cohort study

Table 2 Legionnaires’ disease attack rates and relative risks among residents of an apartment complex for seniors (n = 143 respondents)

Characteristics	No. of LD patients	No. of non-patients	Attack rate	Relative risk^*(95% confidence interval)
Overall	8	135	4.7%^†	--
Potable water exposures
Any showering	8	90	8.2%	7.02 (0.45–128.21)
Any tub baths	1	70	1.4%	0.13 (0.02–1.09)^‡
Smoking
Current	2	12	14.3%	3.02 (0.67–13.58)
Former (>100 cigarettes)	3	57	5.0%	1.07 (0.22–5.08)
Comorbid condition
Asthma	0	16	0%	0.48 (0.03–7.10)
Chronic lung disease	0	9	0%	1.02 (0.07–18.76)
Chronic kidney disease	0	11	0%	0.74 (0.04–10.46)
Diabetes mellitus	1	51	1.9%	0.45 (0.03–1.93)
Heart disease	1	35	2.8%	0.42 (0.05–3.27)
Immunocompromised^§	2	13	13.3%	3.33 (0.71– 15.70)

^* Relative risk (RR) compares attack rates for persons with and without the exposure or risk factor. RRs were estimated by adding 0.5 to cells with zero values (asthma, and chronic lung or kidney disease).
^† Overall attack rate based on all residents (n = 171), including non-respondents.
^‡ P < 0. 05.
^§ Immunosuppressive therapy, human immunodeficiency virus (HIV) infection, or organ transplant.

ISSN: 1471-2334