Source of infection in young infants hospitalized with Bordetella pertussis

Background: Despite pertussis vaccination, very young infants have the highest rates of morbidity and mortality caused by the microorganism. Aim: To determine the source of Pertussis infection in infants aged six months or less in Chile. Material and Methods: Twenty six household contacts of 10 young infants hospitalized with confirmed Pertussis were studied for the presence of Bordetella Pertussis by polymerase chain reaction (PCR). Clinical and demographic data were analyzed. Results: Respiratory symptoms were present in 20 (77%) contacts, being cough the most common. Pertussis cases were identified in every household and in 18 (72%) of the household members. Four members with B.pertussis were asymptomatic. Source of infection was identified in 80% (8/10) of the infant cases with ages ranging from 6 to 62 years. Half of primary cases had positive PR and their cough duration was significantly shorter compared to primary cases with negative PER. Conclusions: B. pertussis transmission to young infants occurred mainly within the household where adults are generally the source of the infection. Risk factors for infant infection are the same as in developed countries. Therefore, the same strategies, such as routine vaccination in adolescents and adults or cocoon strategy, will help to prevent this disease in infants. (Rev Med Chile 2011; 139: 448-454).