An outbreak of legionellosis linked to a contaminated bath house, June 2000 - Ibaraki
(IASR 2000; 21: 188-189)

On June 23, 2000, a hospital reported pneumonia patients suspected of legionellosis to the local health center. It was found that several more individuals were infected with Legionella pneumophila, and they had a common episode of visiting a public bath in Ishioka City. The Ibaraki Prefecture established the investigation team and requested local hospitals to report similar cases.

In total 43 cases (26 males and 17 females, mean age 62.4) were confirmed including 3 fatal cases. Those cases utilized the public bath during May 20 to June 23, and presented fever (38-40C), sputum production, dyspnea, headache, fatigue during June 8 to 23 (incubation period 2-13 days). Two sputum samples yielded L. pneumophila serogroup 1 and its genome was detected from 6 samples by polymerase chain reaction (PCR). L. pneumophila antigen was positive in 7 urine specimens. L. pneumophila serogroup 1 antibody was significantly elevated in 16 cases.

Of 35 environmental samples collected from the public bath, 18 Legionella spp. isolates, including L. pneumophila serogroup 1(7 isolates), 3(1), 5(4), 6(5) and L. micdadei, were cultured. They were collected from the bath water, water filtration parts, filtrated water, and swab on mist sauna.

Two isolates from the cases and 11 environmental isolates showed the same pattern by pulsed-filed gel electrophoresis (PFGE).

Facility S opened on April 7, 2000, and some 16,000 individuals (average 250 visitors per day) utilized the facility until June 23. The facility had 8 baths including 2 indoor baths, a water fall bath, 2 saunas, and 2 outdoor baths. One water supply system was connected with 4 filtration tanks with chloride mixer, but the other one had no disinfection process. Bath water was scarcely changed, and water supply was insufficient. These conditions were supposed to allow the growth of bacteria.

Reported by: Kyoko Mashiko, Haruyasu Nemoto, Noburu Fuzisaku, and Mikio Doy; Ibaraki Prefectural Institute of Public Health

Correspondence: Fax: +81-29-243-9550

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