Two consecutive nationwide outbreaks of listeriosis in France, October 1999-February 2000

In France, listeriosis surveillance is based on mandatory notification of a ll culture-confirmed cases, with systematic typing of isolates and routine collection of the patient's food history. From October 1999 to March 2000, two outbreaks of listeriosis were detected through this enhanced surveillan ce system. In outbreak 1, analysis of the food histories of cases suggested brand X "rillettes," a pate-like meat product, as the vehicle of infection , and the outbreak strain of Listeria monocytogenes was subsequently isolat ed from the incriminated rillettes. In outbreak 2, a case-control study sho wed that consumption of jellied pork tongue was strongly associated with in fection with the outbreak strain (odds ratio = 75.5, 95% confidence interva l: 4.7, 1,216.0). However, trace-back results did not permit incrimination of any particular manufacturer of jellied pork tongue, and the outbreak str ain was not isolated from the incriminated food or from any production site s. Consumption of jellied pork tongue was discouraged on epidemiologic evid ence alone. The consecutive occurrence of these two outbreaks confirms the epidemic potential of listeriosis, even in a context of decreasing incidenc e, and underlines the importance of timely case-reporting and systematic ty ping of human L. monocytogenes strains to allow early detection and separat e investigation of different clusters.