Comparative Risk Assessment of Legionella spp. Colonization in Water Distribution Systems Across Hotels, Passenger Ships, and Healthcare Facilities During the COVID-19 Era
Abstract
1. Introduction
2. Materials and Methods
2.1. Study Design and Sample Collection
2.2. Microbiological Analysis
2.3. Risk Assessment and Statistical Analysis
2.4. Multivariate Logistic Regression
3. Results
3.1. Legionella Positivity and Temporal Trends
3.2. Serogroup Distribution and Facility Colonization Risks
3.3. Temporal Evolution, Positivity Trends and Post-COVID Risk Profile
Hotels: Post-COVID Risk Profile
3.4. Environmental Risk Factors and Relative Risk Analysis
3.5. Multivariable Analysis Results
4. Discussion
4.1. Facility-Specific Colonization Patterns
4.2. Serogroup Distribution and Environmental Risk Indicators
4.3. Temporal Trends and the COVID-19 Effect
4.4. Strengths and Limitations
4.5. Public Health Implications
5. Conclusions
Supplementary Materials
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Facility | Total Samples | Close Point | Far Point | Direct | Indirect | Cold Water | Hot Water |
---|---|---|---|---|---|---|---|
Public Hospitals | 440 (40.70%) | 27 (6.1%) | 39 (8.9%) | 244 (55.5%) | 178 (40.5%) | 245 (55.7%) | 196 (44.5%) |
Hotels | 239 (22.11%) | 15 (6.3%) | 21 (8.8%) | 128 (53.6%) | 101 (42.2%) | 133 (55.6%) | 106 (44.4%) |
Passenger Ships | 176 (16.28%) | 11 (6.3%) | 16 (9.1%) | 102 (58.0%) | 74 (42.0%) | 98 (55.7%) | 78 (44.3%) |
Primary Health Care Units | 114 (10.55%) | 7 (6.1%) | 10 (8.9%) | 66 (57.9%) | 48 (42.1%) | 63 (55.6%) | 51 (44.4%) |
Private Clinics | 112 (10.36%) | 6 (5.9%) | 10 (8.9%) | 60 (53.6%) | 47 (42.0%) | 62 (55.7%) | 50 (44.3%) |
Total | 1081 (100%) | 66 (6.1%) | 96 (8.9%) | 600 (55.5%) | 436 (40.3%) | 600 (55.5%) | 481 (44.5%) |
Facility | Number of Samples | Total Positive Samples (>50 CFU/L) | 95% CI (Wilson) | <103 CFU/L | ≥103 and <104 CFU/L | ≥104 CFU/L |
---|---|---|---|---|---|---|
Public Hospitals (tertiary-level care) | 440 | 204 (46.36%) | 41.76–51.03% | 125 (28.40%) | 71 (16.13%) | 8 (1.81%) |
Private Clinics | 112 | 24 (21.42%) | 14.84–29.91% | 17 (15.17%) | 7 (6.25%) | 0 |
Primary Health Care | 114 | 98 (85.96%) | 78.41–91.17% | 56 (49.12%) | 19 (16.66%) | 23 (20.17%) |
Hotels | 239 | 91 (38.08%) | 32.15–44.37% | 55 (23.01%) | 24 (10.04%) | 11 (4.60%) |
Passenger ship | 176 | 65 (36.93%) | 30.15–44.27% | 50 (28.40%) | 4 (2.27%) | 11 (6.25%) |
Total | 1081 | 482 (44.59%) | 303 (28.03%) | 125 (11.56%) | 53 (4.90%) |
Sample Type | Number of Samples (n) | Positive (%) | 95% CI |
---|---|---|---|
Hot water (total) | 481 | 52.28% | 47.7–56.8% |
└─ Direct outlet | 258 | 50.71% | 44.6–56.7% |
└─ Indirect outlet | 206 | 50.00% | 43.1–56.9% |
└─ Far away point | 50 | 48.00% | 34.4–61.9% |
└─ Close point | 32 | 34.37% | 19.6–52.2% |
Cold water (total) | 600 | 47.72% | 43.7–51.8% |
└─ Direct outlet | 342 | 39.18% | 34.0–44.5% |
└─ Indirect outlet | 230 | 36.08% | 29.8–42.8% |
└─ Far away point | 46 | 23.80% | 13.1–38.2% |
└─ Close point | 34 | 28.00% | 14.4–45.9% |
Facility | Total Positive Samples (n, %, 95% CI) | L. pneumophila SG1 (n, %, 95% CI) | SG2–15 (n, %, 95% CI) | Other Legionella spp. (n, %, 95% CI) |
---|---|---|---|---|
Hotels | 91 (18.88%, 15.6–22.6%) | 27 (29.60%, 20.7–40.6%) | 66 (72.53%, 62.4–81.1%) | 6 (6.59%, 3.0–13.6%) |
Passenger ships | 65 (13.49%, 10.6–16.9%) | 24 (36.92%, 26.0–49.4%) | 41 (63.08%, 50.6–74.0%) | 0 (0.00%, 0.0–5.52%) |
Primary Health Care | 98 (20.33%, 17.0–24.0%) | 21 (21.43%, 14.2–30.9%) | 80 (81.63%, 73.0–88.1%) | 0 (0.00%, 0.0–3.69%) |
Private Clinics | 24 (4.98%, 3.4–7.1%) | 7 (29.17%, 14.9–49.2%) | 17 (70.83%, 50.8–85.1%) | 0 (0.00%, 0.0–14.25%) |
Public Hospitals | 204 (42.32%, 38.8–45.9%) | 95 (46.57%, 39.8–53.5%) | 111 (54.41%, 47.4–61.0%) | 7 (3.43%, 1.7–6.9%) |
Total | 482 (44.59%, 40.6–48.6%) | 174 (36.09%, 31.8–40.5%) | 315 (65.35%, 61.0–69.5%) | 13 (2.70%, 1.6–4.6%) |
Risk Factor | Odds Ratio (Cross Product) | Odds Ratio (MLE) | Risk Ratio (RR) | Risk Difference (RD%) | p-Value |
---|---|---|---|---|---|
Free residual chlorine < 0.2 mg/L | 2.2213 | 2.2175 | 2.2175 | 18.6545 | <0.0001 |
Cold water temperature > 20 °C | 1.8589 | 1.8569 | 1.5179 | 13.5437 | 0.01 |
Hot water temperature < 50 °C | 6.5394 | 6.5073 | 2.054 | 41.5504 | <0.0001 |
Hot water temperature < 35 °C | 4.7365 | 4.7202 | 3.5792 | 22.3196 | <0.0001 |
Turbidity (non-compliant) | 2.5662 | 2.5639 | 2.5313 | 1.3503 | 0.04 |
Direct water sample (vs. outlet) | 0.9341 | 0.9342 | 0.9610 | −1.6562 | 0.29 |
Sampling at distal (far) outlet point | 1.3534 | 1.3504 | 1.1124 | 6.8915 | 0.22 |
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Papadakis, A.; Koufakis, E.; Chaidoutis, E.A.; Chochlakis, D.; Psaroulaki, A. Comparative Risk Assessment of Legionella spp. Colonization in Water Distribution Systems Across Hotels, Passenger Ships, and Healthcare Facilities During the COVID-19 Era. Water 2025, 17, 2149. https://doi.org/10.3390/w17142149
Papadakis A, Koufakis E, Chaidoutis EA, Chochlakis D, Psaroulaki A. Comparative Risk Assessment of Legionella spp. Colonization in Water Distribution Systems Across Hotels, Passenger Ships, and Healthcare Facilities During the COVID-19 Era. Water. 2025; 17(14):2149. https://doi.org/10.3390/w17142149
Chicago/Turabian StylePapadakis, Antonios, Eleftherios Koufakis, Elias Ath Chaidoutis, Dimosthenis Chochlakis, and Anna Psaroulaki. 2025. "Comparative Risk Assessment of Legionella spp. Colonization in Water Distribution Systems Across Hotels, Passenger Ships, and Healthcare Facilities During the COVID-19 Era" Water 17, no. 14: 2149. https://doi.org/10.3390/w17142149
APA StylePapadakis, A., Koufakis, E., Chaidoutis, E. A., Chochlakis, D., & Psaroulaki, A. (2025). Comparative Risk Assessment of Legionella spp. Colonization in Water Distribution Systems Across Hotels, Passenger Ships, and Healthcare Facilities During the COVID-19 Era. Water, 17(14), 2149. https://doi.org/10.3390/w17142149