Incidence of pertussis in subjects aged 50years and older in France in 2013-2014.

OBJECTIVE: To assess the incidence of pertussis (whooping cough) in subjects aged 50years and older in France.

METHODS: Participating family physicians (FPs) using the patient record management software AxiSanté® included patients aged 50years and older, who had signed an informed consent form, presenting with persistent cough for 7 to 21days. Bordetella genetic material was detected by polymerase chain reaction (PCR) on nasopharyngeal samples collected at the FP's discretion.

RESULTS: A total of 42 FPs included 129 patients from June 2013 to August 2014 (large cities: 38; medium-sized cities: 57; rural areas: 34); 106 samples were analyzed. Overall, 30 pertussis cases were diagnosed: 10 cases confirmed by PCR, 18 purely clinical cases, and two direct epidemiological cases. The crude incidence rate per 100,000 patients aged≥50years was 103.6 (95% CI: 69.9-47.9): 77.1 in large cities, 103.1 in medium-sized cities, and 143.9 in rural areas. The extrapolated incidence rate per 100,000 persons aged≥50years was 187.1 (95% CI: 126.2-67.1): 131.1 in large cities, 256.1 in medium-sized cities, and 242.2 in rural areas.

CONCLUSION: The population aged 50years and older can serve as a reservoir. Its role in Bordetella pertussis circulation should be taken into account for pertussis booster vaccination programs.