RESUMO
INTRODUCTION: Whooping cough is a re-emerging disease. We describe the investigation of an outbreak of whooping cough and the measures of control adopted. METHODS: The event was reconstructed through a longitudinal study of incidence. In addition to the notified cases, an active search from the list of those who attended summer camps was made through telephone calls. An epidemiological survey was applied to all cases; vaccination history was confirmed with computerised clinical history and the obtaining of samples for analytical confirmation was proposed. The description of the outbreak was made through the epidemic curve, the attack rates, the relative risk and the linear trend by ages and the vaccination coverage. RESULTS: Of the 30 cases that appeared, 22 (73.3%) were among the members of the summer camps. In these, the attack rate was 21.8%, 26.7% among the children and adolescents increasing linearly with the age. The large majority (86.4%) of this last group were correctly vaccinated, including the fifth dose at the age of 4-6 years. Through the meticulous study of the first cases and the telephone calls to those who attended the summer camp, 90% of the cases of the outbreak were detected. CONCLUSIONS: The active search of cases allowed an outbreak of whooping cough with a high attack rate to be studied in children and adolescents with a high vaccination coverage, and the application of control measures that contributed to stop the outbreak.