Table 2.
Unadjusted odds ratios and 95% confidence intervals of macro-level demographic and environmental factors and increased odds of legionellosis occurrence
| Incidence ratea | Standard clusterb | Reliable, high-risk clusterc | ||||
|---|---|---|---|---|---|---|
| OR | 95% CI | OR | 95% CI | OR | 95% CI | |
| % ≥ 65 years of age | ||||||
| < 10 | – | – | – | |||
| ≥ 10 to < 15 | 1.10 | 0.88–1.37 | 0.60 | 0.44–0.81 | 0.45 | 0.30–0.67 |
| ≥ 15 | 0.84 | 0.66–1.07 | 0.49 | 0.35–0.69 | 0.33 | 0.20–0.53 |
| % non-white race | ||||||
| < 10 | – | – | – | |||
| ≥ 10 to < 50 | 1.00 | 0.79–1.26 | 0.81 | 0.57–1.17 | 0.89 | 0.54–1.47 |
| ≥ 50 | 1.67 | 1.28–2.17 | 2.67 | 1.86–3.83 | 3.07 | 1.87–5.02 |
| % hispanic ethnicity | ||||||
| < 5 | – | – | – | |||
| ≥ 5 to < 20 | 1.19 | 0.96–1.48 | 0.66 | 0.49–0.88 | 1.05 | 0.70–1.58 |
| ≥ 20 | 1.08 | 0.84–1.39 | 0.47 | 0.32–0.67 | 0.78 | 0.47–1.28 |
| % poverty | ||||||
| < 5 | – | – | – | |||
| ≥ 5 to < 15 | 1.34 | 1.09–1.65 | 1.87 | 1.34–2.62 | 1.40 | 0.86–2.25 |
| ≥ 15 | 1.49 | 1.17–1.90 | 3.78 | 2.68–5.32 | 5.04 | 3.24–7.84 |
| % less or some high school | ||||||
| < 5 | – | – | – | |||
| ≥ 5 to < 10 | 1.24 | 0.99–1.55 | 1.22 | 0.85–1.75 | 1.52 | 0.92–2.48 |
| ≥ 10 | 1.30 | 1.04–1.62 | 2.35 | 1.70–3.25 | 2.70 | 1.72–4.25 |
| % homes built pre-1950 | ||||||
| < 5 | – | – | – | |||
| ≥ 5 to < 20 | 1.45 | 1.17–1.80 | 4.93 | 3.02–8.06 | 4.08 | 2.24–7.43 |
| ≥ 20 | 1.48 | 1.13–1.92 | 9.93 | 5.97–16.50 | 6.58 | 3.50–12.35 |
| % homes built pre-1970 | ||||||
| < 15 | – | – | – | |||
| ≥ 15 to < 35 | 1.58 | 1.25–2.00 | 2.22 | 1.45–3.40 | 1.72 | 1.02–2.91 |
| ≥ 35 | 1.78 | 1.32–2.42 | 5.33 | 3.35–8.49 | 3.94 | 2.21–7.04 |
| % renter occupied | ||||||
| < 10 | – | – | – | |||
| ≥ 10 to < 55 | 1.06 | 0.84–1.34 | 1.41 | 0.96–2.09 | 1.50 | 0.86–2.61 |
| ≥ 55 | 1.40 | 1.08–1.82 | 2.97 | 2.00–4.42 | 4.02 | 2.31–7.00 |
| % vacant housing | ||||||
| < 5 | – | – | – | |||
| ≥ 5 to < 10 | 0.85 | 0.69–1.04 | 1.42 | 1.04–1.95 | 1.81 | 1.16–2.82 |
| ≥ 10 | 1.22 | 0.96–1.56 | 2.54 | 1.82–3.55 | 3.58 | 2.27–5.66 |
| Primary water sourced | ||||||
| Groundwater | – | – | – | |||
| Surface water | 0.77 | 0.60–1.00 | 0.80 | 0.56–1.15 | 0.90 | 0.56–1.45 |
Missing values were excluded from analysis
Values in italics are statistically significantly at a significance level of 5%
Ecological study design at the census tract level
aAge- and sex-adjusted incidence greater or equal to 2 cases per 100,000 persons
bSignificant cluster with 50% of population at risk, relative risk greater or equal to 2 cases per 100,000 persons
cExposed census tracts defined as RR > 2 and reliability score > 0.5
dPopulation-weighted centroids of census tracts were joined with public water system polygons