An outbreak of airborne tularaemia in France, August 2004

Fifteen tularaemia cases were identified after a holiday spent at a converted mill in the Vendee region in France, between 9 and 12 August 2004. The mill was visited, and descriptive, retrospective cohort and environmental investigations were conducted. The 39 people who had stayed at the mill between 24 July and 11 August were asked about symptoms, exposure to food and animals, and leisure activities. A case was defined as a person with evidence of fever and a positive serology (seroconversion or significant rise in antibody titre, or a single titre) = 40. Culture for Francisella tularensis and polymerase chain reaction (PCR) diagnosis was carried out for drinking water, firewood, and domestic animals at the mill. Fifteen cases of tularaemia (38%) were confirmed. Twelve of the cases (80%) had the pulmonary form. None of the patients was admitted to hospital. There was a strong association between infection and participation in a dinner at the mill on 4 August (p<10-8). One of the three dogs present in the dining room was serologically positive for F. tularensis. Results of analysis of environmental samples were negative. These investigations confirmed the occurrence of a cluster of 15 tularaemia cases, in patients who were infected on the evening of 4 August, in a mill in Vend¨¦e, an endemic area for tularaemia. The investigations highlight the existence of nonspecific and benign pulmonary forms of the illness in France. The pulmonary form of infection in the human cases and the positive serology of the dog suggest contamination by inhalation of contaminated particles from the dog¡¯s fur disseminated by the dog shaking itself.