Microbiologic Studies on Young Infants With Lower Respiratory Tract Disease

Viral infections account for most lower respiratory tract infections in young infants (less than 60 days of age). Respiratory syncytial and parainfluenza 3 virus infections accounted for approximately three fourths of the identified virus infections. Other agents were isolated infrequently. Overall, viruses were recovered from 21% of the infants with pneumonia and 25% of the infants with bronchiolitis. Sixteen (18.0%) of 89 infants from whom paired sera were collected had diagnostic antibody rises. Four of five infants with bacteremia also had virus infections. Viral infections of the respiratory tract may play a role in the dissemination of bacterial disease.