Epidemic of légionellose, 
Pas-de-Calais, 
November January 2003-, 2004.  

Community grouped cases of légionellose, Pas-de-Calais , France ,

November 2003 - January 2004 

Pierre-Henry Miquel1, Sylvie Haeghebaert1, Didier Che2, Christine Campese2, Cecile Guitard3, Max Thérouanne3, Guillaume Panié4, Sophie Jarraud5, Daniele Ilef1

 1Cellule interregional of Northern epidemiology (Northern Wax, Lille) 2 Institute of medical day before, Department of the infectious diseases (InVS) 3 departmental Direction of the medical and social businesses (Ddass) 4 regional Direction of industry, research and the environment (Drire) 5 national Center of reference of légionelles (CNRL)

  ALARM

November 28, 2003 ,

 Ddass of Pas-de-Calais was informed by the hospital of Lens of occurred, of two Community cases of légionellose. 

These two cases had domiciled in the commune of Harnes with 400m of distance and the date of beginning of the signs was respectively November the 11, and 15 2003.

The regional Management of the industry of research and the environment (Drire), contacted by Ddass the same day, announced that, mid-November, its services had been informed of an important contamination (106 Unit forming colonies per liter - UFC/l)) by Legionella pneumophila of the cooling towers (TAR) of a petrochemical company located at Harnes. This contamination had been detected at the time of two self-checkings carried out the 15/10 and the 20/11 and one plan of fight against the contamination had been put in?uvre by the company as of knowledge of the results. Occurred of 2 cases of légionellose at residents of Harnes and the discovery of an important contamination of the coolant circuits of a company, distant of less than one kilometres of the place of residence of the cases led Ddass to immediately seek other cases near the general practitioners of the sector and Hospital complex (CH) of Lens. 

December 2, on the whole 9 cases of légionellose were listed. 

All resided at Harnes and in the communes bordering, and had dates of beginning of the signs in November 2003. An epidemiologic investigation was initiated at once by Ddass and Wax in order to confirm the epidemic nature of the phenomenon, to measure the importance, to identify the origin and the source of the contamination and to put of it in?uvre adapted measurements of control.

 METHOD

 A descriptive epidemiologic investigation was carried out in order to generate assumptions into the source of the contamination. 

A case was defined like a person lying or having carried out displacements in a zone of 12 kilometers around Harnes in the 10 days preceding the beginning by the disease. The cases presented, between November 1, 2003 and on January 31, 2004 , an episode of radiologically confirmed pneumopathy, they answered definition of the confirmed or probable case of légionellose of the obligatory declaration [ 1 ].

 Only the cases infected by Legionella pneumophila of sérogroupe 1 were attached to the epidemic. The nosocomiaux cases some, hospitalized during the totality of the incubation period (10 days) were excluded. A retrospective and prospective search of the cases was carried out near the hospitals of the area of Lens and other hospitals referents of the area. 

Each case or, failing this, a person of its close entourage, was questioned by telephone using a standardized questionnaire, bearing on the circumstances of occurred of the disease, the antecedents medical, the way of life, the professional and personal exposures potential to the residence and at the time of displacements in the 10 days preceding the beginning by the symptoms. 

Environmental surveys aiming at identifying the potential sources of contamination were carried out by Drire and Ddass in parallel with the epidemiologic investigation in the 53 communes located in a radius of 12km around Harnes: 

- the installations at the potential risk were checked and census by the services of Drire and Ddass: TAR, other systems of climatisation/refrigeration, stations of washing of cars, the public drinking water network, private and industrial drillings, stations of purification, jets d'eau and decorative fountains, machines of cleaning of the networks of cleansing and the roadway systems and channels; 

- iterative taking away for research the légionelles ones were carried out on all these installations, until the extinction of the epidemic; 

- controls were carried out on the domestic hot water circuits in the residence of all the cases. 

The species of clinical and environmental origin were characterized and compared between them with the national Center of reference of légionelles (CNRL) by the molecular technique of typing in field pulsated after macro restriction of ADN (PFGE).

 Models of dispersion of plume of droplets were developed by Ineris according to the climatic and technical data of an installation at the risk suspected within sight of the first resultants[2 ].

 An experimental method of measurement of concentration of Legionella in the air was installation by the scientific and technical Center of building (CSTB)[2 ]. The data were analyzed with the software Epi Information 6.04d, the cartography was carried out with ArcView 3.

 Results

 On the whole, 86 confirmed cases of légionellose due to Legionella pneumophila 1, occurred of November 5, 2003 to January 22, 2004 , at people lying or having carried out displacements in the area of Lens. Seventeen cases (20%) died. The median age of the cases was 75 years [ min-max:32-92 ] and sex ratio H/F was 1,5. The median time between the date of beginning of the signs and the date of the diagnosis was 4 days [ min-max:0-37 ]. Eighteen cases (21%) required a respiratory assistance.

One or more individual factors supporting occurred of a légionellose were found at 78 cases (92%): consumption of alcohol (51%), diseases cardiovascular (51%), nicotinism (34%), silicosis (20%), chronic bronchitis (17%). The aspect of the epidemic curve, evolving/moving in two successive waves, suggested the assumption of an intermittent and persistent source of contamination (figure 1). All the cases resided or had attended places located in a radius of 12 km around Harnes in the ten days preceding the beginning by the symptoms. Fifty of them (58%) resided or had carried out displacements with Harnes or in the four communes bordering on Harnes.

No place of frequentation, commun run to all the cases, n'a been able to be identified.

 The total rate of attack on the zone of the 22 communes of residence of the cases was 3,9 per 104 inhabitants.

The highest rates of attack were found in the commune of Harnes (23 case; 16,7/104) and 2 neighbouring communes: Annay (5 cases; 10,5/104) and Fouquières-les-Lens (7 cases; 10,1/104) (figure 2). With 23 case and the highest rate of attack among the residents, the commune of Harnes seemed the epicentre of the epidemic (figure 2). Forty-nine cases profited from bronchial taking away. 

A species of Legionella pneumophila sérogroupe 1 was insulated at 23 of them (47%), that is to say at 27% of the whole of the cases. All the clinical speciess presented the same profile genomic after electrophoresis in pulsated field. 

This epidemic species was isolated at the cases during totality from the epidemic (figure 1). The profile of this epidemic species was not identified beforehand in the collection of speciess of the CNRL Research the légionelles ones on the medical hot water supply network in the residence of the cases appeared positive at 5 cases (5,8%). The isolated species were different from the epidemic species, the concentrations lay between 50 and 3 900 000 UFC/L.

 On the whole, 33 companies operating of the TAR were identified in the zone of the investigations. Two of them presented, for the period of study, of the concentrations into légionelles higher than 10/5. These installations were the subject of immediate corrective measurements: stop of the installations, disinfection and weekly follow-up. With the exit of the environmental investigations, the epidemic species was found only on the factory site of company N (TAR, lagoon and muds of sowing of the lagoon), in a station of washing of cars and in the TAR of another factory, both located at Harnes and distant of less than one kilometres of company N (Table 1).

  Table 1 Sites in which the epidemic species was isolated

 Complementary environmental investigations led in company N highlighted since October 15, 2003, of the episodes of high contamination (10/6) by Legionella of the TAR, repeating in spite of measurements of disinfections put in by the company. In the atmospheric taking away carried out by the CSTB with 270m of the lagoon, with surface aerators under operation, a concentration of Legionella of 330 UFC/m³ was found; after the stopping of the aerators it was not found the légionelles ones in the atmosphere [ 2 ].

 Work of modeling of the emissions of aerosols starting from company N suggests that, although decreasing clearly beyond 2km of the transmitting source, the risk of exposure of the populations to aerosols the légionelles ones could exist in a perimeter of about 10 km around the factory [ 3 ].

  These assumptions are supported by the fact that the epidemic species was insulated among patients who had not approached with less 10km a company N.

 Discussion

 This epidemic of légionellose is the most important Community epidemic ever described in France , in term of duration, geographical extension and a number of implied cases. It occurred in a population partially weakened by the silicosis, which could contribute to the importance of the epidemic [ 4 ].

 The speed of the setting in?uvre, as of the alarm, of the coordinated investigations epidemiologic, microbiological and environmental made it possible to identify three environmental sources, located at Harnes, transmitting of the epidemic species: company N, a company of agroalimentary and a station of washing of cars. Nevertheless, the concentrations into légionelles raised in the installations of the agroalimentary company and the station of washing were quite lower (10/2 and <10/3 with those raised in the installations of company N In addition, the fact that the epidemic species was not found in the TAR of the agroalimentary company at the initial stage of the investigations and the architectural configuration of the station of washing make not very probable their implication in which has occurred of this epidemic. On the other hand, the proximity of these installations with company N (less 1km with flight of bird) could explain their secondary colonization by the epidemic species emitted by the installations of company N. However, in spite of the complete stop of the installations of this company as of December 3, 2003 and of new procedures of disinfection, a recrudescence of the epidemic was observed starting from mid-December.

 The results of the investigations suggest that the operations of cleaning to high pressure (carried out from the 8 to December 17), a recontamination of the TAR starting from the system of ventilation of surface of the lagoon, sown by the biological muds contaminated by the epidemic species and a new atmospheric diffusion by the TAR (according to December 20 at January 3), probably contributed to the continuation of the epidemic. On the whole, the results of the epidemiologic, environmental and microbiological investigations suggest that this epidemic is ascribable to an air contamination starting from the systems of cooling of company N contaminated by the légionelles ones. The arguments in favour are: - geographical distribution of the cases with the most important rates of attack in the commune of Harnes and the communes neighbouring;

 - the description of a persistent contamination of the installations of cooling of company N;

 - the description, twice (28/11 and 31/12), of the epidemic species in the TAR of company N; - the similarity of the profiles genomic of the speciess of clinical origin and environmental, insulated in company N;

 - temporal distribution of the case coinciding with the various processes at the risk put in?uvre in company N:

 operation of the contaminated TAR, operations of cleaning, restarting of the installations;

 - and the progressive extinction of the epidemic since the complete stop of all the identified activities at the risk in company N, The alliance of descriptive epidemiology, the environmental investigations and molecular microbiology made it possible to put forth assumptions argued and early as for source of the epidemic.

 This epidemic documents for the first time in France the implication of industrial facilities in occurred of Community cases of légionellose. In France , an exposure at the risk was identified or suspectée in only 43% of the cases of légionellose declared in 2002 and one éco-géo-epidemiologic study, carried out in France in 2002, found a significant increase in the incidence of the légionellose in the communes lodging of the transmitting industrial sources of aerosols [ 5 ].

 The important geographical dispersion of the cases, observed in this epidemic, was never described before. The weather conditions (winds, hygroscopy) and the topology of the area (zone of semi-urban plain) probably contributed to a broad diffusion of aerosols contaminated by the légionelles ones. Perhaps complementary investigations analytical currently in hand, fascinating of account the weather factors, will make it possible to consolidate the assumptions generated by work of modeling of the emissions or will suggèreront other assumptions of research. The fact that the epidemic occurred in winter period also constitutes a notable characteristic. Indeed, whereas the epidemics of légionellose described to date in France and having for origin of the TAR, are all occurred in estival period (June at September) [ 6 ], the species responsible for the epidemic of the area lensoise seems to have a resistance particular to climatic conditions not very favourable with the development of the légionelles ones.

In conclusion, the lesson of the investigation of this epidemic suggests the need for a reinforcement of the actions of prevention, management and evaluation of the risk of légionellose related to the industrial TAR. Collective disease prevention passes by the exhaustive census of the installations at the risk, the improvement and the diffusion of the good practices of maintenance to the owners and the maintenance firms, the reinforcement of the follow-up of the installations at the risk, the strict application of the official recommendations in the event of contamination, the information of the medical authorities in the event of important contamination of installations at the risk, and the reinforcement of the vigilance of the medical authorities around the potential sources of Community contaminations

 References

 [ 1 ] Medical institute of day before, the new device of monitoring of the notifiable diseases, January 2003.

 [ 2 ] Caster hammer E, Mathieu L, measurements of légionelles in the stack disposals of industrial facilities, report/ratio CSTB- Inserm, February 2004.

 [ 3 ] Rouil L, Evaluation of the atmospheric dispersion of aerosols potentially contaminated in the area of Lens. Ineris; February 2004.

 [ 4 ] N N Tran Minh, F Ganiayre, N Lapidus et al.. Community grouped cases of légionellose, Pas-de-Calais , France , investigation case-witnesses, 2003-janvier2004 November, BEH 2004, to appear.

 [ 5 ] Che D, Decludt B, Campese C, Desenclos JC. Sporadic boxes of community acquired legionnaires' disease: ecological study to identify new sources of contamination. J Epidemiol Community Health. 2003 Jun; 57(6): 396-7 ].

 [ 6 ] Medical institute of day before. Special number devoted to the légionellose. BEH 2002; 30-31; 152-155.

 Figure 1 Distribution tri-day labourer of the cases of légionellose according to the date of beginning of the symptoms. Epidemic of légionellose, Pas-de-Calais, November 2003-January 2004.

Figure 3
Case of légionellose according to the date of beginning of the clinical signs. Pas-de-Calais, November 2003-January 2004

   Figure 2 
Distribution géoréférencé of the cases according to the address in the commune of residence.

Epidemic of légionellose, Pas-de-Calais, November January 2003-, 2004.