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Outbreak of Legionnaires

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					 An Outbreak of Legionnaires’
Disease in NHS Greater Glasgow
and Clyde and NHS Lanarkshire
             2011
 Dr Sonya Scott
 StR Public Health NHS GGC
 sonyascott@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) organisational
1. There is a need to improve
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?

				
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