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Legionnaires Disease Associated with a Whirlpool Spa Display -- Virginia, September-October, 1996

MMWR 46(04);83-86

Publication date: 01/31/1997

Table of Contents


Editorial Note



Number of cases of Legionnaires disease, by date of onset ...


Contaminated whirlpool spas have been reported as a source of legionellosis. This report describes the preliminary findings of an ongoing investigation by the Virginia Department of Health (VDH) and CDC of a recent outbreak of Legionnaires disease in Virginia, which implicated a whirlpool spa display at a retail store as the source of infection.

On October 15, 1996, a district health department in southwestern Virginia contacted the Office of Epidemiology, VDH, about a hospital (hospital A) report that 15 patients had been admitted during October 12-13 with unexplained pneumonia. On October 21, another hospital (hospital B), located approximately 15 miles from hospital A, reported its pneumonia census to be higher than expected for the first 2 weeks of October. On October 23, the district health department was informed about three area residents with legionellosis (with Legionella pneumophila serogroup 1 {Lp1} antigen detected in urine); one was a patient at hospital A, and two were patients at hospitals outside the jurisdiction of the health department.

To identify all outbreak-associated cases, investigators reviewed medical records and laboratory reports of admissions to the three hospitals for pneumonia during September 1-November 12. Hospital personnel and area health-care providers collected and submitted specimens from patients with pneumonia, including serum for the determination of acute Lp1 antibody titers (to be followed by convalescent titers); sputum, when possible, for Legionella culture; and urine to detect Lp1 antigens.

A case of Legionnaires disease was defined as pneumonia in an area resident with onset of illness during September 1-November 12 with Lp1 identified by culture of sputum, antigen assay of urine, or fourfold rise in serum antibody titers. Based on the review of records, 23 cases eventually were identified, including 15 by urine antigen, seven by serology, and three by sputum culture; two were identified by urine antigen and sputum culture. Of the 23 case-patients, 22 were hospitalized, and two died. The mean age of case-patients was 65 years (range: 42-86 years), and most (17) were male. Although patients had onsets of illness during September 29-October 22, most (18 {78%}) had onsets during October 8-14 (Figure 1).

To identify potential exposures associated with Legionnaires disease, case-patients were asked about their activities during the 2 weeks before onset of illness. Based on these interviews, a questionnaire was developed and a case-control study was initiated on November 2 to assess potential risk factors for and exposures related to infection. Three controls were selected for each confirmed case by using office records of the primary-care physicians of the case-patients; controls were matched by age (within 10 years), sex, and underlying medical conditions. All case-patients and controls were asked whether, during the 2 weeks before onset of illness, they had visited any of 14 retail and manufacturing sites.

Of the 23 cases, 15 were included in the case-control study (one person died before the case-contol study was initiated and had no available exposure history, and seven patients were identified after convalescent serum became available 2 months following the case-control study). A history of having visited a large home-improvement center during the 2 weeks before onset of illness was reported by 14 (93%) of the 15 cases, compared with 12 (27%) of the 45 controls (matched odds ratio {MOR}=23.3; 95% confidence interval {CI}=3.0-182). Of the 13 case-patients and 12 controls who had visited the store and for whom there was a detailed in-store exposure history, cumulative duration of total store visits averaged 79 minutes for cases, compared with 29 minutes for controls (F-test pless than 0.01); in addition, 10 (77%) case-patients reported spending time in the area surrounding the spas during their visits to the store, compared with three (25%) of the 12 controls (MOR=5.5; 95% CI=0.7-256). Four of these case-patients and one of the controls reported only "walking by" the spa. No other activity, including drinking from the store's water fountains or visiting the 14 other locations in the community, was associated with illness.

Samples were collected and cultured for the presence of Legionella from water sources in the home-improvement center, including a whirlpool spa basin, spa filters, a greenhouse sprinkler system, a decorative fish pond and fountain, potable water fountains, urinals, and hot and cold water taps in the store's restrooms. In addition to these potential sources, a second whirlpool spa had been sold, drained on October 9, and removed from the store floor on October 11. Three filters were available for testing from the two spas. One of these filters was from the purchased spa, and the other two had been used in the spa that was in operation until October 28, but that had been drained and out of service during October 9-17. Lp1 was isolated from the filter from the purchased spa; that isolate was an exact match, by monoclonal antibody sub- typing and arbitrarily primed polymerase chain reaction, to the sputum isolates cultured from two of the cases. A third isolate from the case-patient that did not visit the home-improvement center had a different monoclonal antibody pattern. All other environmental sources, including the other two filters, tested negative.

Reported by: J Hershey, MD, B Burrus, V Marcussen, J Notter, K Watson, R Wolford, RE Shaffner III, New River Health District; Carilion Giles Memorial Hospital, Pearisburg; Carilion Radford Community Hospital, Radford; Columbia Lewis Gale Hospital, Salem; Columbia Montgomery Regional Hospital, Blacksburg; Department of Veterans Affairs Medical Center, Salem; E Barrett, DMD, D Woolard, MPH, L Branch, R Hackler, B Rouse, L Gibson, S Jenkins, VMD, J Rullan, MD, G Miller, Jr, MD, State Epidemiologist, Virginia Dept of Health; S Curran, Div of Consolidated Laboratory Svcs, Richmond, Virginia. Laboratory Corporation of America. Childhood and Respiratory Diseases Br, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases; State Br, Div of Applied Public Health Training (proposed), Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: Approximately 10,000-15,000 cases of Legionnaires disease occur each year in the United States; most occur sporadically (1). Investigations of outbreaks have documented aerosol transmission of Legionella from contaminated cooling towers and evaporative condensers (2,3), showers (4), decorative fountains (5), humidifiers (6), respiratory therapy equipment (7), and whirlpool spas (8). However, the proportion of sporadically occurring disease attributable to these sources has not yet been determined.

In contrast with other spa- or whirlpool-associated outbreaks, in this outbreak, none of the case-patients actually entered the water. Instead, all were most likely exposed by walking by or spending time in the area surrounding the spa. Although most community-wide outbreaks of legionellosis have resulted from transmission from an outdoor source (e.g., cooling towers), this report underscores the potential for such outbreaks in association with contaminated indoor sources.

Even though the epidemiologic findings of the case-control study indicated that the source of the outbreak was located in a home-improvement center, the laboratory findings were critical in identifying the exact source of exposure within the store. Case-patients were more likely than controls to have reported exposure to the spas, but the difference was not statistically significant. By matching the two clinical Lp1 isolates to the isolate from the purchased spa, molecular epidemiologic typing helped link the spa to illness.

Enhanced surveillance during investigations of legionellosis outbreaks may result in the detection of some sporadically occurring cases. For example, in the investigation of this outbreak, one case-patient did not report visiting the home-improvement center. However, the sputum Lp1 isolate from this patient did not match that of the whirlpool spa filter or the other available clinical isolates, suggesting this case was not related to the outbreak.

Although the source of the outbreak was removed before the investigation was initiated, cases continued to occur. However, all of these cases, except the case not related to the outbreak, occurred within the normal incubation period for Legionnaires disease (i.e., 2-10 days) following removal of the source.

Following the investigation, VDH recommended that whirlpool spas being used as displays be regularly inspected and maintained with biocides and that filters be regularly changed or decontaminated. In response to a recent outbreak of Legionnaires disease on a cruise ship (8), CDC developed guidelines for the maintenance of whirlpool spas on cruise ships (9). Based on the findings of this investigation, CDC is assessing these guildelines to determine whether modifications are necessary regarding use of land-based whirlpool spas, including those that are being operated while on display.



  1. Marston BJ, Lipman HB, Breiman RF. Surveillance for Legionnaires' disease: risk factors for morbidity and mortality. Arch Intern Med 1994;154:2417-22.
  2. Dondero TJ Jr, 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.
  3. Breiman RF, Cozen W, Fields BS, et al. Role of air sampling in the investigation of an outbreak of Legionnaires' disease associated with exposure to aerosols from an evaporative condenser. J Infect Dis 1990;161:1257-61.
  4. Breiman RF, Fields BS, Spika JS, Sanden GN, Volmer L, Meier A. Association of shower use with Legionnaires' disease: possible role of amoebae. JAMA 1990;263:2924-6.
  5. Fenstersheib MD, Miller M, Diggins C, et al. Outbreak of Pontiac fever due to Legionella anisa. Lancet 1990;336:35-7.
  6. Mahoney FJ, Hoge CW, Farley TA, et al. Community wide outbreak of Legionnaires' disease associated with a grocery store mist machine. J Infect Dis 1992;165:736-9.
  7. Mastro TD, Fields BS, Breiman RF, Campbell J, Plikaytis BD, Spika JS. Nosocomial Legionnaires' disease and use of medication nebulizers. J Infect Dis 1991;163:667-71.
  8. Jernigan DB, Hofmann J, Cetron MS, et al. Outbreak of Legionnaires' disease among cruise ship passengers exposed to a contaminated whirlpool spa. Lancet 1996;347:494-9.
  9. National Center for Environmental Health/National Center for Infectious Diseases. Final recommendations to minimize transmission of Legionnaires' disease from whirlpool spas on cruise ships. Atlanta, Georgia: US Department of Health and Human Services, Public Health Service, CDC, 1996.
|                     Erratum: Vol. 46, No. 4                              |
|                     =======================                              |
|   SOURCE: MMWR 46(15);336   DATE: Apr 18, 1997                           |
|                                                                          |
|        In the article "Legionnaires Disease Associated with a            |
|   Whirlpool Spa Display -- Virginia, September-October, 1996," the       |
|   publication date for reference 9 was incorrect. The correct            |
|   reference is                                                           |
|   9. National Center for Environmental Health/National Center for        |
|      Infectious Diseases. Final recommendations to minimize              |
|      transmission of Legionnaires' disease from whirlpool spas on cruise |
|      ships. Atlanta, Georgia: US Department of Health and Human Services,|
|      Public Health Service, CDC, 1997.                                   |


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Figure 1

Number of cases of Legionnaires disease, by date of onset ...

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