Outbreak Report: Legionnaires’ disease, Swansea
Agencies:
Public Health Wales
Communicable Disease Surveillance Centre Wales
Health and Safety Executive
City and County of Swansea Council
Carmarthenshire County Council
Bridgend County Council
Neath Port Talbot County Borough Council
Environment Agency Wales
Abertawe Bro Morgannwg University Health Board
Hywel Dda Health Board
Co-authors: Rosalind Reilly, Specialty Registrar, Public Health Wales.
Angela Jones, Locum Consultant in Health Protection, Public Health Wales.
Date: 9 November 2010 / Version: V2 (anonymised) (FINAL)
Distribution:
· Welsh Assembly Government
· Communicable Disease Surveillance Centre
· Individuals affected
· Outbreak team organisations
· Health Protection Agency (Colindale)
Review Date: Not applicable
Purpose and Summary of Document:
An outbreak of Legionnaires’ disease was detected in January 2010 in four residents of Carmarthenshire, Swansea and Bridgend. A multi agency Outbreak Control Team was established to investigate and control the outbreak. This report describes the investigation and control measures that were implemented in this outbreak.
Work Plan reference: Not applicable
Contents
Outbreak Report: Legionnaires’ disease 1
1 Introduction / Background 4
2 Investigation 4
2.1 Case definition 4
2.2 Case ascertainment 5
2.3 Descriptive Epidemiology 5
2.4 Microbiological 5
2.4.1 Human 5
2.4.2 Environmental 5
2.5 Environmental 6
2.5.1 Domestic supplies 6
2.5.2 Industrial and commercial premises 6
2.5.3 Weather 6
3 Results 6
3.1 Descriptive Epidemiology 6
3.2 Microbiology 7
3.2.1 Human 7
3.2.2 Environmental 7
3.3 Environmental 7
3.3.1 Domestic supplies 7
3.3.2 Industrial and commercial premises 8
3.3.3 Weather 8
4 Control measures 9
5 Conclusion 9
6 Summary of results 9
7 Recommendations 10
8 Appendices 10
8.1 Appendix 1 Minutes of OCT meetings 10
8.1.1 Minutes of meeting 12th February 2010 10
8.1.2 Minutes of meeting 18th February 2010 16
8.1.3 Minutes of meeting 25th February 2010 25
8.1.4 Minutes of meeting 25th March 2010 31
8.1.5 Minutes of meeting 26th May 2010 35
8.2 Appendix 2 List of investigated premises February to March 2010 40
8.3 Appendix 3 List of investigated premises May 2010 46
9 References 47
1 Introduction / Background
Legionnaires’ disease is an illness characterised by pneumonia, diarrhoea and fever and is caused by the bacterium Legionella pneumophila. The reservoir for L. pneumophila is environmental water and associated wet soils and it is transmitted to humans via inhalation of aerosolised water. It is not transmitted from person to person. Water systems that lead to the aerosolisation of water such as cooling towers, whirlpool spas and sprinkler systems have a higher risk of contaminating the surrounding air. Cases often have a history of travel within or outside the United Kingdom (Hawker et al. 2005).
Three notifications of Legionnaires’ disease were received by the Mid and West Wales Health Protection Team, Public Health Wales within a 7 day period in early February 2010 in the Swansea and Carmarthenshire area. This was about the same as the expected total for England and Wales in a typical February week. An outbreak control meeting was convened on 12th February 2010 as a result of these notifications. This led to a further case from the Bridgend area with an onset date of 7th December 2009 being reviewed and subsequently included in the outbreak. Two further cases from South East Wales were investigated but were not found to be associated with the four cases in the Swansea outbreak. An investigation into the potential source of this outbreak was undertaken and meteorological data was considered. The outbreak was declared over on 25th March 2010. The outbreak control team reconvened when a further case in Swansea with an onset date of 3rd May 2010 was notified, although this case could not be linked to the four cases in the outbreak following further investigations.
2 Investigation
2.1 Case definition
The case definition was based on time, place and person. This was agreed at the Outbreak Control Meeting on 18th February 2010.
Time: Onset from 1st December 2009.
Place: Case who visited the City of Swansea during incubation period.
Person: A microbiologically confirmed case with no restriction on age or gender.
2.2 Case ascertainment
Cases were ascertained by notifications from Swansea, Carmarthen, and Cardiff (Bridgend resident) Public Health Wales laboratories to the Mid and West Wales Health Protection Team. A further two cases from South East Wales were considered in this investigation following liaison with the South East Wales Health Protection Team. A letter was sent to General Practitioners in Swansea, Carmarthen, Bridgend and Neath Port Talbot to raise awareness of Legionnaires’ disease so that it could be considered as a diagnosis in patients presenting with respiratory symptoms. Consultants in the local hospitals were also alerted. This outbreak was raised in the Five Nations teleconference (England, Scotland, Northern Ireland, Republic of Ireland and Wales) so that any cases with a history of travel to South Wales could be ascertained.
2.3 Descriptive Epidemiology
All cases were contacted by Environmental Health Officers from the relevant Environmental Health Departments. The National Surveillance Scheme for Legionnaires’ disease form was completed for each case along with the All Wales Legionnaires’ disease investigation pro forma. The questions included:
Demographic details including occupation, onset of symptoms, whether pneumonia present, main clinical features, immunosuppression, hospital admission, outcome, whirlpool/spa exposure, travel history and movements in the 14 days before onset.
Where appropriate, electronic and paper logs of cases’ movements were obtained from employers and diaries.
The cases’ movements were mapped to identify any areas of commonality. As the investigation evolved, travel to the City of Swansea appeared to be a common feature so cases were re-interviewed or further information was obtained on the detailed movements over the 14 days prior to the onset of symptoms.
2.4 Microbiological
2.4.1 Human
Diagnosing doctors of suspected cases of Legionnaires’ disease submitted urine samples to Public Health Wales laboratories for antigen testing for L. pneumophila. Further samples from one case were submitted to Colindale reference laboratory for culture and typing.
2.4.2 Environmental
Five environmental samples from potential sources were submitted for microbiological culture for L. pneumophila during the initial investigation and three further environmental samples were submitted during the further investigation in May 2010.
2.5 Environmental
2.5.1 Domestic supplies
Local Authorities investigated home plumbing installations including taps, showers and boilers with a focus on recent modifications. Sampling of home plumbing installations was considered during the outbreak control meetings but not undertaken during the outbreak. Following the notification of a further case in May 2010, sampling of the domestic supply was undertaken for this case.
2.5.2 Industrial and commercial premises
Information gathered during the initial investigation showed that all four cases had been in the vicinity of the City of Swansea during their incubation period. Possible sources such as cooling towers, premises that emit aerosols, evaporative condensers and scrubbing towers were investigated by the City and County of Swansea Council, Neath Port Talbot Council and the Health and Safety Executive. These agencies investigated how these premises were managed and the City and County of Swansea Council took environmental samples from five premises of interest. The Environment Agency assisted in identifying potential sites and supported the investigation. Following the notification of the additional case in Swansea in May 2010 and recent research indicating a possible link between L. pneumophila and compost, water samples and composting plant samples from three premises to the east of Swansea which use a natural process or manufacture compost were obtained.
2.5.3 Weather
Meteorological data regarding wind patterns around Swansea were provided by the City and County of Swansea Council.
3 Results
3.1 Descriptive Epidemiology
There were 4 cases meeting the case definition as defined above. A further 2 cases with urine antigen positivity for L. pneumophila were considered but neither of these cases had visited the Swansea area during their incubation period. Furthermore, one of these cases was subsequently de-notified by Colindale reference laboratory. One further case was notified after the outbreak was declared over and after investigation was not thought to be connected with the original outbreak. The following is a description of each case:
Case 1: Onset 18th January 2010. Male (35-39 years) from Carmarthenshire. Exposure: 11th January 2010 visited Cwmdu in Fforestfach, Swansea. 13th January 2010 visited Trostre retail park, Llanelli. Regular visits to Industrial Estate in Pembrokeshire. No recent plumbing work at home, no car wash use. No travel history.
Case 2: Onset 27th January 2010. Female (45-49 years) from Swansea. Exposure: Visited a number of premises in Swansea city centre, and a premise in Enterprise Park during incubation period. No travel history.
Case 3: Onset 25th January 2010. Male (40-44 years) from Swansea. Exposure: 18 January 2010 visited Mount Pleasant and Llansamlet. 20th January 2010 visited range of areas around Swansea. Driver route records showed he visited the Enterprise Park and numerous locations around Swansea city centre. Visited car wash during incubation period.
Case 4: Onset 7th December 2009. Male (45-49 years) from Bridgend. Exposure: 1st December 2009 travelled to Killay from Briton Ferry via Fabian Way and through Swansea city centre. Did not stop during this journey. No other visits to Swansea during incubation period.
Case 5: Onset 31st January 2010. Case has only been to East side of Cardiff and not visited Swansea at all during incubation period. Excluded.
Case 6: Onset 19th December 2009. Case denotified by HPA. Excluded.
Case 7 (referred to as Case 5 in minutes of outbreak control team meeting on 26th May 2010): Onset 3rd May 2010. Male (50-54 years) from Swansea. Exposure: Had stayed in Swansea city centre during incubation period and visited a static caravan in South West England from 30th April-3rd May 2010. Excluded (the outbreak was declared over on 25th March 2010, when this case was notified it was investigated for epidemiological and microbiological links to cases 1-4 but no links to these cases could be found other than a geographical link).
3.2 Microbiology
3.2.1 Human
All four cases were positive for urine antigen L. pneumophila serogroup1.
Typing was successful for Case 2 only – ‘group 1 monoclonal subgroup Allentown/France sequence type 46’.
3.2.2 Environmental
No results positive for L. pneumophila were obtained from the environmental samples submitted.
3.3 Environmental
3.3.1 Domestic supplies
It was agreed by City and County of Swansea Council, Carmarthenshire County Council and Bridgend County Council that no sampling of domestic appliances was undertaken due to the outbreak situation and likelihood of a common source. Domestic samples were obtained from the home of Case 7 (referred to as Case 5 in minutes of outbreak control team meeting on 26th May 2010) and were negative for L. pneumophila. The following information was obtained about domestic appliances for Cases 1-4:
Case 1 – No plumbing work recently carried out at home. Shower used on daily basis.
Case 2 – No information obtained.
Case 3 – No plumbing work recently carried out at home. Combi boiler serviced in September 2009. No immersion heater or hot water tanks. New shower installed in August 2009 and used daily.
Case 4 – No plumbing work recently carried out at home. Tank in attic, immersion heater, no condenser boiler.
3.3.2 Industrial and commercial premises
Local Authorities and HSE identified premises in Swansea that were registered as having cooling towers. Enquiries were also made about any other premises that may emit aerosols in the Swansea area.
Premises within a 10 kilometre radius of Swansea city centre were investigated. The area of investigation included the west side of Neath Port Talbot industrial area and south east of Swansea due to meteorological data obtained (see 3.3.3 below). A total of 43 premises (see Appendix 2) with the potential to emit aerosols were investigated (either contacted or visited). Potential sources included cooling towers, evaporative condensers, wet scrubbing towers, and car washes. In addition, information about air conditioning units on two ships being refurbished were obtained from the Chief Environmental Health Officer Swansea Port Health Authority, but these were decommissioned before docking. No other likely sources on the docks were identified. The three premises investigated in May 2010 are shown in Appendix 3. One premise was the same as one of the 43 investigated initially, but a different process was tested.
Five environmental samples were submitted during the outbreak but no results positive for L. pneumophila were obtained. The further environmental samples sent from three composting sites were also negative.
3.3.3 Weather
The predominant wind direction in Swansea is south westerly. The wind direction in Swansea 6 days (median incubation period) prior to the onset of each case was easterly, south easterly i.e.
Case 1 – 6 days prior to onset on 12th January 2010: Strong easterly, south easterly winds
Case 2 – 6 days prior to onset on 21st January 2010: south easterly winds
Case 3 – 6 days prior to onset on 19th January 2010: Moderate easterly, south easterly winds
Case 4 – 6 days prior to onset on 1st December 2009: Strong easterly, south easterly winds
NB. Case 7 was excluded but similar east, south easterly wind patterns occurred during incubation period.
4 Control measures
1) General Practitioners in the area were sent a letter to raise awareness of the symptoms of Legionnaires’ disease.
2) Consultants in the local hospital were alerted to the outbreak to raise awareness and to encourage testing for Legionnaires’ disease.
3) Outbreak raised in Five Nations Health Protection teleconference to discuss importance of reporting to us any cases in other nations who have a history of travel to South Wales.
4) Potential source premises were investigated and enforcement action was taken on three premises and advice about systems or record keeping given to several premises.
5 Conclusion
This outbreak of Legionnaires’ disease consisted of four cases who had been in the Swansea area during their incubation period. Six days before the onset of their illness, all had been in Swansea and there were south easterly winds, which differs from the prevailing wind direction of south westerly. A thorough investigation into potential sources in industrial and commercial premises took place, with priority focused on premises south east of the city. No source of L. pneumophila was identified but awareness in these premises was raised as well as the importance of complying with regulations.