Update: Outbreak of Legionnaires' Disease Associated
with a Cruise Ship, 1994
On July 15, 1994, CDC was notified by the New Jersey State
Department of Health of six persons with pneumonia who had recently
traveled to Bermuda on the cruise ship Horizon (1). In conjunction
with local and state health departments, an investigation was
initiated; as of August 10, a total of 14 passengers had
Legionnaires' disease (LD) confirmed by either sputum culture (one
patient), detection of antigens of Legionella pneumophila serogroup
1 (Lp1) in urine by radioimmunoassay (seven patients) (2), or
fourfold rise in titer of antibodies to Lp1 between acute- and
convalescent-phase serum specimens (six patients). Possible cases
in 28 other passengers with pneumonia that occurred within 2 weeks
after sailing aboard the Horizon are under investigation. Cases
have occurred from nine separate week-long cruises during April 30-
July 9, 1994.
To identify the source of Legionella sp., a case-control study
was conducted, and environmental sampling of the ship's water
system was performed. Exposure to the whirlpool baths was strongly
associated with illness (odds ratio=16.4; 95% confidence
interval=3.7-72.3). Cultures taken from a sand filter used for
recirculation of whirlpool water yielded an isolate of Lp1; this
isolate and the clinical isolate had matching monoclonal antibody
subtyping patterns (3).
A variety of interventions were completed, including
hyperchlorination of the ship's potable water supply, removal of
the whirlpool filters, and discontinuation of the whirlpool baths.
Following completion of these interventions, on July 30 the Horizon
resumed its weekly sailing schedule from New York City to Bermuda.
Reported by: I Guerrero, MD, Community Medical Center, Toms River;
C Genese, MJ Hung, S Paul, MD, H Ragazzoni, DVM, J Brook, MD, L
Finelli, PhD, KC Spitalny, MD, State Epidemiologist, New Jersey
State Dept of Health. BA Mojica, MD, KJ Mahoney, MSW, RT Heffernan,
MPH, Div of Disease Intervention, New York City Dept of Health; SF
Kondracki, DL Morse, MD, State Epidemiologist, New York State Dept
of Health. ML Cartter, MD, J Hadler, MD, State Epidemiologist,
Connecticut Dept of Public Health and Addiction Svcs. JT Rankin,
Jr, DVM, State Epidemiologist, Pennsylvania Dept of Health. C
Groves, MS, Maryland State Dept of Health and Mental Hygiene. Div
of Quarantine, National Center for Prevention Svcs; Office of the
Director, National Center for Environmental Health; Div of Field
Epidemiology, Epidemiology Program Office; Childhood and
Respiratory Diseases Br, Div of Bacterial and Mycotic Diseases,
National Center for Infectious Diseases, CDC.
Editorial Note
Editorial Note: This outbreak represents the first documented
instance of LD aboard a cruise ship docking in U.S. ports.
Whirlpool spas previously have been associated with transmission of
Legionella (4,5); hyperchlorination of water systems and
replacement of filter devices have successfully terminated
outbreaks of LD linked to whirlpool spas. CDC recommends
post-intervention environmental sampling of whirlpool circulation
systems in conjunction with ongoing surveillance for cases of
pneumonia to ensure the efficacy of these interventions. Suspected
cases of LD among Horizon passengers should be reported to CDC
through state and local health departments.
Additional recommendations to reduce the transmission of
Legionella sp. from whirlpool baths and aboard cruise ships will be
the subject of a special meeting of public health officials, LD
experts, and members of the whirlpool and cruise line industries;
the meeting is tentatively scheduled for the fall of 1994 in
Atlanta. Additional information about the meeting is available from
CDC's Office of the Director, National Center for Environmental
Health, telephone (404) 488-7093.
References
CDC. Outbreak of pneumonia associated with a cruise ship, 1994.
MMWR 1994;43:521.
Kohler RB, Zimmerman SE, Wilson E, et al. Rapid radioimmunoassay
diagnosis of Legionnaires' disease: detection and partial
characterization of urinary antigen. Ann Intern Med 1981;94:601-5.
Joly JR, McKinney RM, Tobin JO, Bibb WF, Watkins ID, Ramsay D.
Development of a standardized subgrouping scheme for Legionella
pneumophila serogroup 1 using monoclonal antibodies. J Clin
Microbiol 1986;23:768-71.
Vogt RL , Hudson PJ, Orciari L, Heun EM, Woods TC. Legionnaires'
disease and a whirlpool spa {Letter}. Ann Intern Med 1987;107:596.
Spitalny KC, Vogt RL, Orciari LA, Witherell LE, Etkind P, Novick
LF. Pontiac fever associated with a whirlpool spa. Am J Epidemiol
1984;120:809-16.
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