Factors That Affect Legionella Positivity in Healthcare Building Water Systems from a Large, National Environmental Surveillance Initiative

Legionella growth in healthcare
building water systems can result in legionellosis, making water management
programs (WMPs) important for patient safety. However, knowledge is
limited on Legionella prevalence in
healthcare buildings. A dataset of quarterly water testing in Veterans
Health Administration (VHA) healthcare buildings was used to examine
national environmental Legionella prevalence
from 2015 to 2018. Bayesian hierarchical logistic regression modeling
assessed factors influencing Legionella positivity. The master dataset included 201,146 water samples from
814 buildings at 168 VHA campuses. Overall Legionella positivity over the 4 years decreased from 7.2 to 5.1%, with the
odds of a Legionella-positive sample
being 0.94 (0.90–0.97) times the odds of a positive sample
in the previous quarter for the 16 quarters of the 4 year period.
Positivity varied considerably more at the medical center campus level
compared to regional levels or to the building level where controls
are typically applied. We found higher odds of Legionella detection in older buildings (OR 0.92 [0.86–0.98] for each
more recent decade of construction), in taller buildings (OR 1.20
[1.13–1.27] for each additional floor), in hot water samples
(O.R. 1.21 [1.16–1.27]), and in samples with lower residual
biocide concentrations. This comprehensive healthcare building review
showed reduced Legionella detection
in the VHA healthcare system over time. Insights into factors associated
with Legionella positivity provide
information for healthcare systems implementing WMPs and for organizations
setting standards and regulations.