In 2008 and 2009, a community-based hepatitis A outbreak spread throughout the Nord department. Epidemiological surveillance helped identify the factors contributing to transmission and allowed for the adaptation of control measures. A total of 492 confirmed cases were reported, including 157 in 2008 and 335 in 2009. Five outbreak clusters were observed. The median age of cases was 9.5 years [min–max: 1.5–87] and the hospitalization rate was 28%. The source of infection was linked to active person-to-person transmission within families or close social circles (45%), in communities living in poor sanitary conditions (26%), and within childcare settings (17%). The virological investigation revealed the complex circulation, during the epidemic, of genotype IA strains belonging to three phylogenetic clusters. In addition to strengthening hygiene measures, controlling the outbreak required the implementation of collective strategies (vaccination campaigns among populations living in poor sanitary conditions) and individual strategies (vaccination of family members of cases), in accordance with the recommendations of the High Council for Public Health dated February 13, 2009. This episode illustrates the epidemic risk posed by the virus and the value of vaccination among contacts of confirmed cases. (R.A)