Objective: To study the possible viral etiology in 139 infants with lower respiratory tract infection who required hospitalization in the Infant Unit of our hospital, from October 1994 to June 1995.
Patients and methods: 139 patients were admitted, aged from 13 days to 14 months, during this period. The etiological agent was detected by direct immunofluorescence from nasopharyngeal secretions. Monoclonal antibodies were used against Respiratory Syncitial Virus, Influenza A Virus, Influenza B Virus, Adenovirus and Parainfluenza 3 Virus. Antibody detection against these viruses by Complement Fixation Test was done on 29 of these patients, with paired sera (acute and convalescent phase).
Results: In 82 patients (59%) we found at least one viral agents from the nasopharyngeal specimens, but in 64 of these only one was detected, in the remaining 18, there were more than one. Significant levels of antibodies were detected in only six of the 29 patients tested. Serology was negative in the remaining 23 patients.
Conclusions: Syncitial Respiratory Virus is the first virus responsible for the lower respiratory tract infection in this age group (49%). There was no correlation between serological diagnosis and antigen detection.