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Cluster of legionnaires’ disease cases in northern France, the situation on 17 December 2003

Christine Campese (c.campese@invs.sante.fr) and Didier Che, on behalf of the investigation team*.

* S. Haeghebaert, F. Ganiayre, D. Ilef, Cellule Inter-Régionale d’Epidémiologie-Nord; M. Thérouanne, C. Guitard, T. Brigaud, Direction Départementale des Affaires Sanitaires et Sociales, Pas-de-Calais; and C. Campese, D. Che: Institut de Veille Sanitaire, Saint-Maurice, France.

An outbreak involving twenty four cases of legionnaires’ disease has been reported/notified in northern France (the Nord Pas de Calais) since 28 November 2003.

All patients have been admitted to hospital. Nineteen of the patients are men (79%). The patients’ ages range from 44 to 87 years (mean age 71 years). Onset of symptoms for all cases is between 10 November and 12 December 2003. Three patients have died. The diagnosis of legionnaires’ disease has been confirmed for all cases by the detection of urinary antigen. Clinical isolates have also been obtained from three patients, and these have been sent to the Centre National de Référence (CNR) des Legionella (national reference centre for Legionella).

Figure. Distribution of cases of legionnaires’ disease in the Pas-de-Calais, by date of onset of symptoms, November-December 2003. Source: InVS.

The epidemiological investigation is being carried out by the local health authorities, with support from the Institut de Veille Sanitaire (http://www.invs.sante.fr). All patients were asked to complete a questionnaire giving details of their habits and their movements in the ten days preceding the appearance of symptoms, (maximum incubation period for legionnaires’ disease is 10 days). According to information gathered, most of the patients were resident in or visited an area to the east of the town of Lens (Harnes and neigbouring communes). This information suggests a common local source, such as a cooling tower or similar.

The environmental investigation is underway, and control measures have already been taken at sites that pose a possible risk (disinfection of cooling systems). One factory in Harnes is under suspicion after environmental samples revealed elevated levels of Legionella, and it was closed on 3 December for disinfection of the cooling system and its cooling tower. The other sites that might pose a risk have been inspected, and all environmental samples have been sent to the Legionella CNR for analysis. Additionally, the local health authorities, in collaboration with the local town councils, are compiling a register of all sites posing a possible risk.

Comparison of clinical and environmental samples is underway, and will allow investigators to determine if one of the potential sites identified is the source of contamination.