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Legionnaire’s Disease Outbreak (point source): Stoke on Trent, 2012. Dr Nic Coetzee (West Midlands North HPU) -- on behalf of the Outbreak Control Team. December 2012. Stoke-on-Trent. Phil Taylor. The start. Friday 20 th July 2012 2 cases notified – lab UHNS: interviews

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legionnaire s disease outbreak point source stoke on trent 2012

Legionnaire’s Disease Outbreak (point source):Stoke on Trent, 2012

Dr Nic Coetzee (West Midlands North HPU)

-- on behalf of the Outbreak Control Team

December 2012

the start
The start...

Friday 20th July 2012

  • 2 cases notified – lab UHNS:
    • interviews
  • 6-10 cases/ year average - Staffordshire
  • Internal incident meeting
    • No specific risk factors
    • Enhanced case finding
    • Cooling towers (LA, HSE)
week 1
Week 1...

Cum. cases

week 11
...Week 1...

Cum. cases

week 12
...Week 1...

Cum. cases

week 13
...Week 1...

Cum. cases

week 14
...Week 1

Cum. cases

microbiological investigation
Microbiological Investigation
  • Testing - all patients with ? pneumonia at UHNS
  • Neg & pos samples == Colindale
  • All 21 patients confirmed Legionella antigen sg 1 positive by reference laboratory Colindale
    • 2 were negative at local laboratory
  • 11 sputum samples - 9 DNA sequence based typing confirmed Legionella pneumophila sg1 ST1268
  • Unique strain, never seen before
case definitions
Case Definitions
  • Confirmed:
    • Clinical/radiological pneumonia
    • Lab conf acute Legionella (Antigen/Culture/PCR/Serology)
    • Onset from 30 June 2012
    • Lived or visited Stoke area in 14 days before onset.
  • Probable:
    • As above + onset date from 2 May 2012.
epidemiological investigation
Epidemiological Investigation
  • 2 HPU Nurses interviewing + re-interviewing all cases;
  • REU staff onsite - HPU EOC:
    • analyse data, direct investigation;
  • Remote analyses - Porton mapping/modelling team;
  • Health Advice Group:
descriptive epi
Descriptive Epi
  • 21 confirmed cases + 2 earlier possible cases re-investigated.
  • All cases live in or around Stoke.
slide21

Source drained

Source confirmed

Exposure

Onset to presentation: 3 – 7 days

is source a registered cooling tower
Is source a registered cooling tower?
  • 7 cooling towers – Stoke; 5 in neighbouring areas; total 8 sampled
  • Stoke cooling towers inspected - HSE/LA when 2 cases reported on weekend of 21-22/7;
  • Inspected & sampled 23-24/7: most already treated;
  • Case histories - “epi fit” - analysed
    • nearest postcode from home, work or place visited
  • Only one tower positive for Legionella:
    • different strain to cases and poor fit epidemiologically.
an unregistered exterior source where
An unregistered exterior source - where?
  • south Stoke - highest risk for external source from home + work postcodes + prevailing winds.
  • >30 sites identified and risk assessed by LA/HSE.
  • 5 sites inspected + sampled (4 negative).
interviews re interviews sites visited by confirmed cases
Interviews, re-interviews:sites visited by confirmed cases
  • All 21 visited JTF Mega discount warehouse;
  • 14 visited The Range retail outlet;
  • 10 visited Tesco Longton;
  • 3 visited Morrisons Festival park;
  • No other site visited more than twice;
  • 3 car washes + 3 hospitals visited by 1 case each.
sites for further investigation
Sites for further investigation
  • JTF, The Range, Aggregate industry, Powder coating , Tesco Longton all identified - visited.
    • JTF - spa bath on open display
    • The Range - indoor fountains: made safe and sampled.
  • Legionella pneumophila sg1 ST1268 found by PCR in 9 cases & sample - spa bath at JTF.
  • Dates of visit obtained for 20 cases:
    • incubation period range 3-14 days, median of 5 days.
environmental investigation summary
Environmental Investigation - summary
  • >30 potential sites plus 12 registered cooling towers
  • 15 sites higher risk, investigated and sampled
    • Rob Johnston (F,W,E lab) with LA or HSE colleague
    • Labour intensive
  • JTF swab sample positive for Legionella pneumophila sg1 ST1268 strain
  • Second site (cooling tower) positive culture Legionella pneumophila SG1but ST62 strain
  • All other sites negative
jtf hot tub most probable source
JTF hot tub - most probable source
  • Identical unique strain – cases & hot tub, - only env source
  • All confirmed cases visited JTF - only
  • Incubation periods - consistent
  • Spa baths - indoor display - known source
  • Spa bath close to the tills/exit, - all visitors passed nearby

JTF retail ‘Mega’ discount store

lessons learnt
Lessons Learnt ...
  • Descriptive epi

– interviews, re-interviews....

  • Case finding – clinical microbiologist, GP
  • Respiratory samples
  • Water samples – rapid, expert, independent
  • Real-time dedicated epi support – line list and mapping
  • Health advice group
  • Genotyping : DNA sequence based typing
lessons learnt1
... Lessons learnt
  • Command & control:
    • Incident director
    • Clinical, environ investigation & OCT chair
    • Media and sitrep – talking head
    • GP liaison and acute desk support
    • Epi team on-site EOC
      • EOC, IT
      • Resilience, operational demand
      • Media pressure, MPs ....
      • Safety – indoor spa pools – public spaces
slide31

Spa pools

(hot spa/ hot tub/ whirlpool spa, “Jacuzzi”)

  • Not swimming – sitting / lying
  • Self-contained body of water - filtered & chemically disinfected.
  • Not drained, cleaned, or refilled after each user
  • Water heated to 30 – 40 deg C
  • Hydrotherapy jet circulation +/- air induction bubbles.