An Outbreak of Legionnaires’ Disease in NHS Greater Glasgow and Clyde and NHS Lanarkshire

2011

Dr Sonya ScottStR Public Health NHS GGCsonyascott@nhs.net

What I’ll Cover

Legionellosis Timeline of Events The Investigation Lessons Learned and

Recommendations

Legionellosis

• Legionellae bacteria

• 3 main requirements for growth and spread.

• Transmission by inhalation

• 2-10 day incubation

• 2 clinical presentations

• LD – 12% case fatality

Event Timeline (1)

• 7 April – possible nosocomial case notified to GGC.

• 16 April – a second case of community acquired LD notified to GGC.

• 26 April – third case of community acquired LD notified post-mortem to GGC.

Event Timeline (2)

• 5 May – Two further cases of community acquired LD

notified to GGC.– PAG convened– HSE and EH begin process of inspecting ECS– Awareness raising partners, clinicians, public.

• 6-11 May– Two further cases notified to NHS GGC, one post-

mortem and one to NHS LN– PAG becomes OCT

Event Timeline (3)• 12-19 May

– Two further cases, one post-mortem, notified NHS GGC and one to NHS LN

– HPA asked to undertake temporal and spatial analysis of case data.

– Inspection of all ECS complete• 20 May - 30 June

– Final case notified to NHS GGC– No epidemiological or microbiological link between

cases found.• No new cases as of 8th July 2011• No common source identified.

The Investigation

Case Definitions

• Clinical/Radiological CAP +• Greater Glasgow Association +• Onset after 1st March +• Confirmed

– + isolate L.sp or seroconversion or urinary antigen or direct PCR full SBT.

• Probable– L.sp. Antigen sputum or lung or direct partial SBT or history

shared setting with confirmed case

• Possible– Direct PCR L.sp. but no SBT or high single titre for L.sp.

Epidemiological Investigation Methods

Three main parallel strands• Standard Trawling questionnaires• Geographical information system• Modelling Work

– Cluster analysis– Statistical calculation of release window– Kernel density analysis– Attack rate analysis

Results of Epidemiological Investigation (1)

• Eight cases GGC three LN

• 7 confirmed cases, 1 probable and 3 possible

• Median age 62y (range 34-84)

• 82% (9) male

• All hospitalised, with requiring ITU

• Smoking, Immunodeficiency common

• 36% case fatality.

Results of Epidemiological Investigation (2)

• Dates of onset 21st March and 2nd June

• Release window 14/3/11 – 28/4/11

• 2 clusters

• Commonality of movement centre Glasgow.

• No specific epidemiological link

Complexities of Epidemiological Picture

• Possibility of hospital acquired case

• Travel Histories

• Concomitant infections

• Occupational Histories

• False positive urinary antigen results!

The Human Microbiological Investigation

• 6 positive urinary antigen results• 3 isolates

– 2 Knoxville, – 1 France/Allentown

• 4 different SBTs• Others

– 2 cases direct positive PCR no SBT– 1 case direct positive PCR partial SBT– 1 case Single high titre L.sp. Not assignable

The Environmental Investigation- Methods

• All domestic water systems sampled

• Occupational water systems sampled

• 57 ECS, across 23 companies inspected

• 23 ECS sampled– Sampling where clustering of movement or

deficiencies

Results of Environmental Investigation

• Poor compliance with code of practice

• Significant failings – 4 companies

• All ECS samples negative for Legionella

• High bromine levels

Lessons and Recommendations (1)

1. There is a need to improve organisational compliance with code of practice for control of Legeionella risk

R: HSE and COSLA to consider regular proactive inspection of regulated water systems to ensure compliance with ACOP.

2. It is difficult to determine the probability of common community source for a cluster of LD in the early stages of an investigation, without access to formal modelling techniques.

R: There is a need to develop accessible technologies to assess cluster probability in an emerging situation.

Lessons and Recommendations (2)

3. Further guidance on the role of water sampling in the investigation of LD is required.

R: To be considered in current revision of guidance by HPN, some interagency training may be required.

4. There is a need to review the role of diagnostic tests in the investigation of clusters and outbreaks of LD.

R: To be considered in current revision of guidance by HPN.

Any Questions?