Outbreak of Legionnaires' disease associated with a display whirlpool spa.

BACKGROUND: Recognized outbreaks of Legionnaires' disease (LD) are rare; when they occur, they provide opportunities to understand the epidemiology of the illness and improve prevention strategies. We investigated a population-based outbreak. METHODS: After the confirmation of LD in October 1996 in five people in neighbouring towns in southwest Virginia, active surveillance for additional cases was undertaken. A case-control study was conducted to identify exposures associated with illness, followed by a cohort study among employees of the facility at which the source of the outbreak was located in order to assess unrecognized exposure and illness. Samples of likely sources of LD in the facility were cultured for LEGIONELLA: RESULTS: In all, 23 laboratory-confirmed cases of LD were eventually identified. Of the 15 cases in the case-control study, 14 (93%) reported visiting a home-improvement store, compared with 12 (27%) of 45 controls (matched odds ratio [MOR] = 23.3; 95% CI : 3-182). Among home-improvement centre patrons, 10 (77%) of 13 cases questioned recalled either visiting or walking by a display whirlpool spa, compared with 3 (25%) of 12 controls (MOR = 5.5; 95% CI : 0.7-256.0). Two cases' sputum isolates were an exact match, by monoclonal antibody subtyping and arbitrarily primed polymerase chain reaction, to a whirlpool spa filter isolate from the store. Employees reporting more exposure to the display spas were more likely to report symptoms of LD or to have an elevated titre. CONCLUSIONS: This investigation shows that LD can be transmitted from a whirlpool spa used for display only, and highlights the need for minimizing the risk of transmission of LD from all water-filled spas. Key messages This paper describes an investigation of a population-based outbreak of Legionnaires' disease (LD). A case-control study first identified a home-improvement store as the likely source of the outbreak. An environmental investigation later confirmed that finding, as two cases' sputum isolates were an exact match, by monoclonal antibody subtyping and arbitrarily primed polymerase chain reaction, to a whirlpool spa filter isolate from the store. The spa was intended and used for display only.

Two pseudo-outbreaks of infectious mononucleosis.

Two outbreaks of suspected infectious mononucleosis (IM) were investigated. In the first outbreak IM was diagnosed in nine children attending a day care center. They had been tested in physicians' offices for heterophile antibody using rapid differential slide tests; all tests had been reported positive. On retesting, none of the suspected cases had detectable serum heterophile antibody. The initial test results had been falsely positive as a result of poor laboratory technique. In the second outbreak IM had been diagnosed in 285 college students. Suspected cases had been found to have serum IgG antibody to the viral capsid antigen of Epstein-Barr virus, but most had not been tested for the presence of heterophile antibody. Retesting of 64 students within 1 month of initial testing yielded only one with heterophile antibody. With the exception of young children (less than 4 years of age), differential slide tests for heterophile antibody are sensitive and specific for recent Epstein-Barr virus infection if properly performed. Viral capsid antigen to Epstein-Barr virus (IgG) titers are of limited usefulness in diagnosing acute IM. The misdiagnosis of IM can be prevented by the appropriate selection, performance and interpretation of diagnostic laboratory tests.

An outbreak of metal fume fever. Diagnostic use of urinary copper and zinc determinations.

An outbreak of metal fume fever (MFF) among workers involved in cutting brass pipes with electric cutting torches in an enclosed, poorly ventilated steam condenser is described. Twenty-six workers were affected. Symptoms most commonly reported were fever (21), dyspnea (23), chills (21), headache (21), and nausea (19). Fourteen of the workers experienced the symptom of an unusual sweet or metallic taste in the mouth. Clinical signs were limited to wheezing or rales in eight patients. Leukocytosis and an increase in band cell forms were noted in 21 and 20 of 24 workers, respectively. The median time interval between exposure and onset of symptoms was five hours. None of three workers who spent less than one hour in the condenser became ill, whereas 25 of 26 of those who spent more than one hour became ill (p = .001). Five of 12 workers had urine copper levels in excess of 0.05 mg/l. To our knowledge, this is the first reported outbreak of MFF for which urinary copper levels have been measured.