Legionellosis -- Staffordshire, England, and Wayne County,
Michigan
The largest reported outbreak of legionellosis outside the
United
States occurred during April and early May 1985 in Staffordshire,
England. During this period, 158 persons were hospitalized with
acute
respiratory infections; 36 (23%) of these cases have been fatal.
To
date, 60 patients have laboratory evidence of legionellosis,
including
11 of the fatal cases. Patients are predominantly elderly, and
most
reside within an 8-10 mile area. The only common exposure noted
among
the 50 confirmed cases was a visit to the Outpatient Department
(OPD)
at the Stafford District General Hospital. A case-control study to
confirm this association and to define specific exposures within
the
OPD is under way. Most visits to the OPD occurred in the week
following Easter vacation. The OPD was not open during the
vacation
period, and the water supply was not circulating at that time.
Samples from the potable water system have been negative for
Legionella to date. There is also a cooling tower from the air
conditioning system in the vicinity of the OPD, and L. pneumophila
serogroup 1 has been isolated from water samples. The cooling
tower
and the potable water system have been chlorinated, and the potable
hot water system temperature has also been increased. No further
cases have occurred.
An outbreak of legionellosis also occurred in Michigan during
early May. Fourteen cases of pneumonia with high fever have been
identified in the approximately 380 persons who attended a church
banquet at a hotel on April 27; three (21%) of these cases have
been
fatal. To date, seven cases have laboratory evidence of
legionellosis, including all the fatal cases. No common exposures
other than attending the banquet have been identified. Samples of
the
hotel's potable water, a nearby swimming pool and whirlpool, and
the
12 functioning heat and ventilation air conditioning units have
been
obtained. Washings obtained from the external surface of the
cooling
coils of both air conditioning units supplying the banquet hall
have
grown L. pneumophila serogroup 1. Passive surveillance of the over
800 persons attending 12 other banquets held at the hotel between
April 25 and May 10 has identified only one suspected case with
pneumonia. No recent cases have been identified.
Reported by The Communicable Disease Surveillance Center, London,
England; KA Tait, MPH, DW Lawrenchuk, MD, V Vangieson, DVM, Wayne
County Health Dept, Michigan, WN Hall, MD, KR Wilcox, Jr, MD,
Michigan
Department of Public Health; Respiratory and Special Pathogens
Epidemiology Br, Div of Bacterial Diseases, Center for Infectious
Diseases, CDC.
Editorial Note
Editorial Note: Legionnaires' disease occurs in epidemic and
sporadic
forms. Sporadic cases outnumber the epidemic cases; an estimated
25,000-50,000 cases of sporadic legionellosis occur in the United
States each year (1). Despite this, the occurrence of large
outbreaks, such as that in Staffordshire, underlines the continuing
public health hazard of epidemic legionellosis. During outbreaks,
attack rates tend to be highest in specific high-risk groups,
including the elderly, smokers, and immunocompromised persons.
Epidemic legionellosis usually results from exposure of
susceptible individuals to an aerosol generated by an environmental
source of water contaminated with Legionella. In previous
outbreaks,
disease has been associated with exposure to evaporative
condensers,
cooling towers, showers, whirlpools, and respiratory therapy
equipment
(2-6). A specific source has not yet been epidemiologically
implicated in either of these recent outbreaks. Recovery of
Legionella from an environmental site does not by itself constitute
proof of the source of the outbreak because Legionella is
frequently
isolated from water sources unrelated to outbreaks of human
disease.
Additional efforts must be made to find an association between
exposure to a given potential source of the organism and occurrence
of
the disease, including appropriate epidemiologic studies, specific
sub-typing of Legionella isolates, and identification of a
mechanism
of aerosol generation that could allow transmission to occur (7).
Further epidemiologic and laboratory investigation of potential
environmental sources is currently under way in both outbreaks.
Routine testing of potable water systems or cooling towers for
L.
pneumophila is of questionable value and, therefore, has not been
recommended, since the organism is ubiquitous, and the significance
of
a positive culture in the absence of associated illness cannot be
defined. In addition, routine decontamination of potable water
systems or cooling towers specifically directed at Legionella is
not
without hazard. Routine treatment with biocides active against
Legionella does not necessarily eradicate the organism (8).
Studies
are under way to determine the settings in which Legionella causes
human disease and to evaluate effective control measures.
References
Foy HM, Broome CV, Hayes PS, Allan I, Cooney MK, Tobe R.
Legionnaires' disease in a prepaid medical-care group in
Seattle
1963-75. Lancet 1979;I:767-70.
Dondero TJ, Rendtorff RC, Mallison GF, et al. An outbreak of
Legionnaires' disease associated with a contaminated
air-conditioning cooling tower. N Engl J Med 1980;302:365-70.
Spitalny KC, Vogt R, Witherell L, et al. Legionnaires' disease
and Pontiac fever associated with a whirlpool. Miami Beach,
Florida: 22nd Interscience Conference on Antimicrobial Agents
and
Chemotherapy, 1982 (abstract #87).
Shands KN, Ho JL, Gorman GW, et al. Potable water as a source
of
Legionnaires' disease. Clin Res 1981;29 (abstract #260A).
Jones E, Checko P, Dalton A, et al. Nosocomial Legionnaires
disease associated with exposure to respiratory therapy
equipment,
Connecticut. In: Legionella. Thornsberry C, Balows A, Feeley
JC, Jakubowski W, eds. Washington D.C.: ASM, 1984:225-7.
Cordes LG, Wiesenthal AM, Gorman GW, et al. Isolation of
Legionella pneumophila from hospital shower heads. Ann Intern
Med
1981;94:195-7.
Broome CV. Epidemiologic assessment of methods of transmission
of
legionellosis. Zbl Bakt Hyg, I. Abt. Orig. A 1983;255:52-7.
Fliermans CB, Harvey RS. Effectiveness of 1-Bromo-3-Chloro-5,
5-Dimethylhydantoin against Legionella pneumophila in a cooling
tower. Applied Environ Microbiology. 1984;47:1307-10.
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