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Volume 23, Number 11—November 2017
Research

Weather-Dependent Risk for Legionnaires’ Disease, United States

Jacob E. Simmering, Linnea A. Polgreen, Douglas B. Hornick, Daniel K. Sewell, and Philip M. PolgreenComments to Author 
Author affiliations: The University of Iowa, Iowa City, Iowa, USA

Main Article

Table 4

Effects of humidity and temperature on Legionnaires’ disease risk, United States, 1998–2011*

Variable Odds ratio 95% CI
Age, y
18–30 1.00 Ref
31–40 2.60 2.30–2.95
41–50 2.23 2.87–3.62
51–60 3.22 2.88–3.61
61–70 2.29 2.04–2.57
71–80 1.74 1.54–1.96
81–90 1.37 1.21–1.55
>91
0.78
0.66–0.93
Race/ethnicity
White 1.00 Ref
Black 1.37 1.31–1.44
Hispanic 1.05 0.96–1.13
Other
1.00
0.93–1.10
Payer
Medicare 1.00 Ref
Medicaid 0.87 0.81–0.93
Private 2.43 2.32–2.53
Uninsured 1.86 1.71–2.03
Other
1.65
1.48–1.83
Sex
M 1.00 Ref
F
0.75
0.73–0.78
Hospital admission mo
Jan 1.00 Ref
Feb 0.85 0.77–0.94
Mar 0.74 0.67–0.82
Apr 0.91 0.82–1.00
May 1.10 0.99–1.23
1.35–1.71
Jun 1.52
Jul 2.24 1.99–2.52
Aug 2.49 2.21–2.80
Sep 2.35 2.10–2.64
Oct 2.58 2.37–2.80
Nov 1.63 1.49–1.79
Dec
1.14
1.04–1.25
Year
1.06
1.06–1.07
Hospital latitude, °N
Latitude 3.06 2.67–3.50
Latitude squared
0.99
0.99–0.99
Total monthly rainfall†
Dry 1.00 Ref
Normal 1.36 1.29–1.44
Wet
1.47
1.38–1.57
Mean monthly temperature, °F
<60 1.00 Ref
60–80 0.55 0.44–0.68
>80
1.57
1.24–1.98
Mean RH, %
0–50.0 1.00 Ref
50.1–55.0 0.85 0.68–1.06
55.1–60.0 0.58 0.48–0.70
60.1–65.0 0.66 0.56–0.78
65.1–70.0 0.79 0.67–0.93
70.1–75.0 0.80 0.68–0.94
75.1–80.0 0.76 0.64–0.90
80.1–100.0
0.65
0.53–0.78
Interactions
Temperature 60°–80°F
RH <50% 1.0 Ref
RH 50.1%–55.0% 1.65 1.19–2.28
RH 55.1%–60.0% 1.54 1.13–2.09
RH 60.1%–65.0% 2.15 1.68–2.75
RH 65.1%–70.0% 2.27 1.83–2.83
RH 70.1%–75.0% 2.93 2.36–3.64
RH 75.1%–80.0% 3.27 2.62–4.08
RH 80.1%–100.0% 4.79 3.71–6.17
Temperatures >80°F
RH <50% 1.0 Ref
RH 50.1%–55.0% 0.00
RH 55.1%–60.0% 0.00
RH 60.1%–65.0% 1.23 0.77–1.95
RH 65.1%–70.0% 0.62 0.42–0.91
RH 70.1%–75.0% 0.38 0.24–0.60
RH 75.1%–80.0% 0.91 0.54–1.54
RH 80.1%–100.0% 0.00

*Based on a multivariable logit model with a diagnosis of Legionnaires’ disease as the outcome variable. The analysis comprised data from 26 states: Arizona, Arkansas, California, Colorado, Connecticut, Illinois, Iowa, Kentucky, Maryland, Massachusetts, Mississippi, Missouri, Montana, Nevada, New Hampshire, New Jersey, New York, North Carolina, Oregon, Pennsylvania, Rhode Island, Utah, Vermont, Virginia, Washington, Wisconsin. Dash indicates 95% CIs not defined because there were no data for cases or controls in that particular strata.
†Dry, <18 mm; normal, 18–85.85 mm; wet, >85.85 mm.

Main Article

Page created: October 16, 2017
Page updated: October 16, 2017
Page reviewed: October 16, 2017
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.
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