LEGIONELLA - World Health Organization

This case highlights the high risk for Legionella pneumonia among bone marrow transplant
patients, and the need to take permanent (rather than intermittent) decontamination measures
to prevent nosocomial L. pneumophila in high-risk patients (Oren et al., 2002).
9.4.3 Hot tub outbreak — Austria
In March 2004, a spatial and temporal cluster of cases of legionellosis occurred in a small area
of northern Austria. The cluster prompted immediate epidemiological and environmental
investigations by the Austrian Agency for Health and Food Safety. Four cases of L. pneumophila,
with onset of illness between 10 and 13 March 2004, were reported to the Austrian Legionella
Reference Centre by hospital laboratories or local health authorities. The cases were all male
and were aged between 28 and 65 years.
In all four cases, pneumonia was diagnosed clinically and by X-ray, and all cases had a confirmed
laboratory diagnosis by detection of L. pneumophila antigen in urine. A significant seroconversion
(more than fourfold) to L. pneumophila serogroup 1 was observed in the first and third cases.
The reference laboratory detected L. pneumophila serogroup 1 by direct fluorescent antibody
staining, and L. pneumophila DNA (deoxyribonucleic acid) by polymerase chain reaction in
the respiratory secretion of the third case. A single, high-specificity serum antibody titre to
L. pneumophila serogroup 1 was found in the fourth case. No isolates were obtained from any
of the cases.
All four patients were hospitalized. The third case, a 65-year-old patient, developed multi-organ
failure and required mechanical ventilation and haemodialysis for 11 days. All cases recovered.
The Federal Ministry for Women and Health announced this cluster of cases of Legionella
infection in a press statement on 31 March 2004. The ministry initiated active case finding
by alerting practitioners and clinicians working in the areas where the cases occurred.
The four cases were linked by area of residence. The timing of clinical onset indicated that all
were exposed to a common source of infection during a restricted period. Interviews with the
patients about their activities during the 10 days before clinical onset revealed that all had
attended a trade fair for energy-saving products, held on 5–7 March 2004 in a city near their
residences. The trade fair included hot tub display stands. All patients reported that they had
visited the hot tub stands at the exhibition.
This information prompted a series of environmental investigations. Water samples were
obtained from the cold and warm water system of the exhibition centre at which the trade
fair was held. Only 5 out of 20 demonstration hot tubs that had been exhibited at the trade
fair were identified and sampled. No legionellae were detected in any water sample.
The epidemiological evidence indicates that the most likely source was one or more hot tubs
at the display. The fact that the microbiological environmental investigations did not confirm
this was probably due to the inevitable delay between exposure and the investigation.
LEGIONELLA AND THE PREVENTION OF LEGIONELLOSIS