WATER AND HEALTH (T WADE, SECTION EDITOR)
Outbreaks of Legionnaires’ Disease and Pontiac Fever 2006–2017
K. A. Hamilton
A. J. Prussin II
C. N. Haas
Published online: 9 May 2018
Springer International Publishing AG, part of Springer Nature 2018
Purpose of Review The global importance of Legionnaires’ disease (LD) and Pontiac fever (PF) has grown in recent years. While
sporadic cases of LD and PF do not always provide contextual information for evaluating causes and drivers of Legionella risks,
analysis of outbreaks provides an opportunity to assess these factors.
Recent Findings A review was performed and provides a summary of LD and PF outbreaks between 2006 and 2017. Of the 136
outbreaks, 115 were LD outbreaks, 4 were PF outbreaks, and 17 were mixed outbreaks of LD and PF. Cooling towers were
implicated or suspected in the a large portion of LD or PF outbreaks (30% total outbreaks, 50% confirmed outbreak-associated
cases, and 60% outbreak-associated deaths) over this period of time, while building water systems and pools/spas were also
Summary Potable water/building water system outbreaks seldom identify specific building water system or fixture deficiencies.
The outbreak data summarized here provides information for prioritizing and targeting risk analysis and mitigation strategies.
Keywords Legionnaires’ disease
Legionnaires’ disease (LD) and the milder form of illness,
Pontiac fever (PF), are respiratory illnesses caused by infection
with the bacteria Legionella spp. Infection results when the
bacteria are inhaled or aspirated. L. pneumophila is the most
common cause of LD and PF . Legionnaires’ disease is a
reportable illness in Europe, the USA, Canada, New Zealand,
Japan, Singapore, and Australia ; however, specific source
attributions or systematized, cross-regional data collection re-
garding water system deficiencies resulting in outbreaks is
sparse. Infections are typically of concern for the elderly and
those with underlying health conditions .
Although there are over 50 species of Legionella anda
growing list of at least 16 serogroups of L. pneumophila ,
the majority of human infections are determined by the pre-
dominant urinary antigen testing to be caused by L.
pneumophila serogroup 1 . However, the dominance of
serogroup 1 may be biased due to the fact that the urinary
antigen test is designed to identify this serogroup [5••].
Therefore, the importance of infections with other serogroups
may be underestimated. L. pneumophila serogroup 1 can be
further distinguished based on subtypes, determined using
monoclonal antibody (MAb) subtyping into monoclonal sub-
groups such as Allentown/France, Bellingham, Benidorm,
Camperdown, Heysham, Knoxville, OLDA, Oxford, and
Philadelphia [6, 7]. Additionally, sequence-based typing
(SBT) using comparison with seven gene loci proposed by
the European Society for Clinical Microbiology Study
Group on Legionella Infections (ESGLI; formerly the
European Working Group on Legionella Infections,
EWGLI) can be used to determine how closely two isolates
are related [5••, 8, 9].
Management of Legionella in water systems is complex as
it occurs commonly in most aquatic environments and sur-
vives readily within biofilms . However, its presence is
not necessarily synonymous with risk, resulting in varied
This article is part of the Topical Collection on Water and Health
Electronic supplementary material The online version of this article
(https://doi.org/10.1007/s40572-018-0201-4) contains supplementary
material, which is available to authorized users.
* K. A. Hamilton
Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104,
Virginia Polytechnic Institute and State University,
Blacksburg, VA 24061, USA
CSIRO Land and Water, Ecosciences Precinct, 41 Boggo Road,
Brisbane, QLD 4102, Australia
Current Environmental Health Reports (2018) 5:263–271