Spread assessment of Legionella in a hospital water system through the geostatistical analysis. 7th European Public Health Conference ”Mind the gap: Reducing healt inequalities in health and health care

Background Legionnaires’ disease is normally acquired by inhalation of legionellae from a contaminated environmental source. Water systems of large buildings, such as hospitals, are often contaminated with legionellae and therefore represent a potential risk for hospital population. The aim of this study was to evaluate the potential contamination of Legionella pneumophila (LP) in a large hospital in Italy through geo-statistical analysis (FAI-K) to assess the possible sources of dispersion and, consequently, the risk of exposure. Methods We considered the diffusion of LP serogroups 1 and 2-14 in the wards housed on two floor overlay of the hospital building. On the basis of information provided by 53 bacteriological analysis, a "random" grid of points has been chosen and a spatial geo-statistics or FAI-k Kriging was applied and compared with the results of classical statistical analysis. Results Over 50% of the examined samples at terminals water points (taps, shower heads, etc.) were positive for LP. LP 1 were isolated in 69% of samples from the ground floor and in 60% of sample from the first floor; LP 2-14 in 36% of sample from the ground floor and 24% from the first one. The iso-estimation maps show clearly the most contaminated pipe and the difference in the diffusion of the different LP serogroups. Conclusions Experimental work has demonstrated that geo-statistical methods applied to microbiological analysis of water matrices allows a better modeling of the phenomenon under study, a greater potential for risk management and a greater choice of methods of prevention and recovery environment to be put in place with respect to the classical statistical analysis. Main Message Geostatistical analysis allows not only to identify parts of the water system contaminated but also to estimate contamination risk of other water points and to prevent exposure of hospital population.