Alert On June 30, 2006, the director of a nursing home in Gironde notified the Gironde Departmental Directorate of Health and Social Affairs (DDASS) of two confirmed cases of pertussis among the facility’s staff. Two residents, awaiting serological testing, also exhibited symptoms suggestive of pertussis. The DDASS had taken initial preventive measures and, on July 10, 2006, notified the Aquitaine Interregional Epidemiology Unit (CIRE) of the ongoing outbreak, requesting methodological support for the investigation to be conducted. On July 11, the Cire began an on-site investigation to confirm and describe the outbreak, with a view to proposing possible recommendations on additional management measures that could be implemented to control the outbreak. Method A cohort-based epidemiological survey was conducted among all residents and staff of the nursing home. Case definitions that were more sensitive than those recommended by the French High Council for Public Health (CSHPF) made it possible to identify and count cases that occurred between May 15 and July 31, 2006. Data collection was performed using residents’ medical records and a standardized questionnaire administered to all individuals meeting the case definition. Microbiological investigation supplemented these data. Results The study included 74 residents and 46 staff members. A total of 13 cases were identified between May 15 and July 13, including 5 residents and 8 staff members, with respective attack rates of 7% and 17%. The epidemic curve was consistent with person-to-person transmission of the disease within the nursing home and identified an index case among the residents. Symptoms, which varied widely depending on the case, ranged from an unusual paroxysmal cough to a nocturnal, sleep-disturbing cough that could lead to significant respiratory difficulties or be accompanied by asthenia. No factors associated with the onset of the disease could be identified. Discussion This is the first reported outbreak of pertussis in a long-term care facility for the elderly in France. The difficulty in detecting pertussis among elderly individuals, who often have multiple comorbidities, and the lack of droplet precautions among staff clearly facilitated the spread of the disease within the facility. This episode confirms that despite high vaccination coverage rates in France, the bacterium is still circulating and can cause outbreaks in adult care facilities. Recommendations The investigation of this outbreak served as a reminder of the importance of testing for pertussis in adults with a persistent cough of no obvious cause, of the rapid implementation of control measures around a case, and, more generally, implementing standard control measures in response to clusters of infectious respiratory illnesses occurring within a community, whether among residents or staff, even before the results of the epidemiological investigation are available.