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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 PCR and their cough duration was significantly shorter compared to primary cases with negative PCR., 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.

Background: The availability of a serologic test for cat scratch disease in humans has allowed the diagnosis of an increasing number of cases of this disease in Chile., Aim: To perform a serological survey for Bartonella henselae among cats in Chile., Material and Methods: Blood samples from 187 cats living in three Chilean cities were obtained. IgG antibodies against Bartonella henselae were measured using indirect immunofluorescence. Blood cultures were done in 60 samples. The presence of Bartonella henselae in positive cultures was confirmed by restriction fragment length polymorphism polymerase chain reaction (RFLP-PCR)., Results: The general prevalence of IgG antibodies against Bartonella henselae was 85.6%. No differences in this prevalence were found among cats younger or older than 1 year, or those infested or not infested with fleas. However domestic cats had a lower prevalence when compared with stray cats (73 and 90% respectively, p <0.01). Bartonella henselae was isolated in 41% of blood cultures. All the isolated were confirmed as Bartonella henselae by RFLP-PCR., Conclusions: This study found an important reservoir of Bartonella henselae in Chilean cats and therefore a high risk of exposure in humans who have contact with them.

Background: Influenza-A (IA) occurs every winter, is mostly observed among outpatients., Aim: To describe the clinical and epidemiological characteristics of cases that required hospital admission during an outbreak in Chile in 1999., Patients and Methods: Adults subjects, with Influenza A confirmed by antigen detection test, hospitalized in the clinical hospital of the "Hospital Clínico de la Universidad Católica de Chile" between May and June, with fever or respiratory symptoms were studied. A special record was designed to register clinical, microbiological and therapeutic data., Results: Fifty five cases, 26 males, aged 15 to 91 years, were studied. Eighty four percent had chronic concomitant diseases and 9.1% were immunosuppressed. Clinical findings were fever in 873%, asthenia in 83.6%, cough in 93.6%, abnormal pulmonary signs in 69%, an elevated C-reactive protein (mean value of 11.6 +/- 7.1 mg/dL) and acute respiratory insufficiency in 54.5%. Cases were isolated in cohort or individual rooms and 38.2% were admitted to intensive or intermediate care units. Amantadine was prescribed to 52 patients and was well tolerated. Thirty three percent of cases developed pneumonia. These subjects were older; had more dyspnea and respiratory insufficiency than patients without pneumonia., Conclusions: IA should be borne in mind when dealing with hospitalized adults, during epidemic outbreaks in the community. The clinical picture can resemble a serious bacterial infection. An early diagnosis allows the use of specific treatments, to decrease the risk of nosocomial spread and to avoid unnecessary use of antibiotics.