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The Stafford outbreak of Legionnaires’ disease

Published online by Cambridge University Press:  15 May 2009

M. C. O'Mahony
Affiliation:
Public Health Laboratory Service Communicable Disease Surveillance Centre, 61 Colindale Avenue, London NW9 5EQ.
R. E. Stanwell-Smith
Affiliation:
Public Health Laboratory Service Communicable Disease Surveillance Centre, 61 Colindale Avenue, London NW9 5EQ.
H. E. Tillett
Affiliation:
Public Health Laboratory Service Communicable Disease Surveillance Centre, 61 Colindale Avenue, London NW9 5EQ.
D. Harper
Affiliation:
Public Health Laboratory Service Communicable Disease Surveillance Centre, 61 Colindale Avenue, London NW9 5EQ.
J. G. P. Hutchison
Affiliation:
Birmingham Public Health Laboratory, East Birmingham Hospital, Bordesley Green East, Birmingham B9 5ST.
I. D. Farrell
Affiliation:
Birmingham Public Health Laboratory, East Birmingham Hospital, Bordesley Green East, Birmingham B9 5ST.
D. N. Hutchinson
Affiliation:
Preston Public Health Laboratory, Meadow Street, Preston PR1 6PS.
J. V. Lee
Affiliation:
Public Health Laboratory Service Centre for Applied Microbiology and Research, Porton Down, Salisbury SP4 0JG.
P. J. Dennis
Affiliation:
Public Health Laboratory Service Centre for Applied Microbiology and Research, Porton Down, Salisbury SP4 0JG.
H. V. Duggal
Affiliation:
Mid–Staffordshire District Health Authority, Corporation Street, Stafford ST16 3SR.
J. A. Scully
Affiliation:
Mid–Staffordshire District Health Authority, Corporation Street, Stafford ST16 3SR.
C. Denne
Affiliation:
Mid–Staffordshire District Health Authority, Corporation Street, Stafford ST16 3SR.
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Summary

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A large outbreak of Legionnaires’ disease was associated with Stafford District General Hospital. A total of 68 confirmed cases was treated in hospital and 22 of these patients died. A further 35 patients, 14 of whom were treated at home, were suspected cases of Legionnaires’ disease. All these patients had visited the hospital during April 1985. Epidemiological investigations demonstrated that there had been a high risk of acquiring the disease in the out patient department (OPD), but no risk in other parts of the hospital. The epidemic strain of Legionella pneumophila, serogroup 1, subgroup Pontiac la was isolated from the cooling water system of one of the air conditioning plants. This plant served several departments of the hospital including the OPD. The water in the cooling tower and a chiller unit which cooled the air entering the OPD were contaminated with legionellae. Bacteriological and engineering investigations showed how the chiller unit could have been contaminated and how an aerosol containing legionellae could have been generated in the U–trap below the chiller unit. These results, together with the epidemiological evidence, suggest that the chiller unit was most likely to have been the major source of the outbreak.

Nearly one third of hospital staff had legionella antibodies. These staff were likely to have worked in areas of the hospital ventilated by the contaminated air conditioning plant, but not necessarily the OPD. There was evidence that a small proportion of these staff had a mild legionellosis and that these ‘influenza–like’ illnesses had been spread over a 5–month period. A possible explanation of this finding is that small amounts of aerosol from cooling tower sources could have entered the air–intake and been distributed throughout the areas of the hospital served by this ventilation system. Legionellae, subsequently found to be of the epidemic strain, had been found in the cooling tower pond in November 1984 and thus it is possible that staff were exposed to low doses of contaminated aerosol over several months.

Control measures are described, but it was later apparent that the outbreak had ended before these interventions were introduced. The investigations revealed faults in the design of the ventilation system.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1990

References

REFERENCES

1.Committee of Inquiry. First report of the committee of inquiry into the outbreak of Legionnaires’ disease in Stafford in April 1985. HMSO Cmnd 9772, 1986.Google Scholar
2.Taylor, AG, Harrison, TG. Serological tests for Legionella pneumophila serogroup 1 infections. Zbl Bakt Hyg 1983; 255: 20–6.Google ScholarPubMed
3.Tillett, HE. Statistical analysis of case–control studies of communicable diseases. Int J Epidemiol 1986; 15: 126–33.CrossRefGoogle Scholar
4.Edelstein, PH. Improved self–selective medium for isolation of Legionella pneumophila from contaminated clinical and environmental specimens. J Clin Microbiol 1981; 14: 298303.CrossRefGoogle Scholar
5.Watkins, ID, Tobin, JO'H, Dennis, PJ, Brown, W, Newnham, R, Kurtz, JB. Serogroup 1 subgrouping by monoclonal antibodies – an epidemiological tool. J Hyg 1985; 95: 211–6.CrossRefGoogle ScholarPubMed
6.Druett, HA, May, KR. Unstable germicidal pollutant in rural air. Nature 1968; 220: 395–6.CrossRefGoogle ScholarPubMed
7.Bartlett, CLR, Bibby, LF. Epidemic legionellosis in England and Wales 1979–82. Zbl Bakt Hyg 1983; 255: 6470.Google Scholar
8.Fischer-Hoch, SP, Bartlett, CLR, Tobin, JO'H et al. , Investigation and control of an outbreak of Legionnaires’ disease in a district general hospital. Lancet 1981; I: 932–6.CrossRefGoogle Scholar
9.Timbury, MC, Donaldson, JR, McCartney, AC et al. , Outbreak of Legionnaires’ disease in Glasgow Royal Infirmary: microbiological aspects. J Hyg 1986; 97: 393403.CrossRefGoogle Scholar
10.Fraser, DW, Tsai, TR, Orenstein, W et al. , Legionnaires’ disease, description of an epidemic of pneumonia. N Engl J Med 1977; 297: 11891203.CrossRefGoogle ScholarPubMed