A surveillance system for acute lower respiratory tract illnesses was implemented February 1977 in five neighborhood health clinics. Of the 1,229 patients with an illness identified during the 25 months from Feb 1, 1977 to Feb 28, 1979, there were 38 with croup, 451 with tracheobronchitis, 339 with bronchiolitis, and 401 with pneumonia. Forty-two percent of the illnesses occurred in children less than 1 year of age and 66% occurred in children less than 2 years of age. A viral infection was diagnosed in 20% of the patients by viral cultures and/or fourfold rises in complement fixation antibody titers in acute and convalescent sera. A viral agent was identified in 29% of patients with croup, 20% with tracheobronchitis, 22% with bronchiolitis, and 17% with pneumonia. Four viral agents, respiratory syncytial virus (RSV) adenovirus, parainfluenza viruses, and influenza viruses accounted for 94% of the cases associated with a viral infection. RSV was associated with 9% of the cases, adenovirus with 6.8%, parainfluenza with 2.1%, and influenza with 1.3%. These four viral agents had slightly different clinical patterns. The majority of RSV infections were diagnosed in children less than 2 years of age with bronchiolitis or pneumonia. Yearly outbreaks of RSV were noted during periods corresponding to RSV peaks in northern temperate climates. Adenoviral infections occurred most frequently in children between 1 and 5 years of age with tracheobronchitis or pneumonia in association with high fever. Parainfluenza viral infections were usually associated with tracheobronchitis and pneumonia. Influenza infections usually occurred in older children with pneumonia associated with high fever, headache, and myalgias. Bacteremias were identified in four patients with lower respiratory tract infections. Twenty percent of children with moderate or severe malnutrition and an acute respiratory illness were bacteremic. Three of the four children with moderate or severe malnutrition, pneumonia, and fever greater than 38.9°C had a positive blood culture. There were 17 children seen who required hospitalization and three subsequent deaths in this group.
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