Patterns of acute respiratory tract infection in children: a longitudinal study in a depressed community in Metro Manila. The incidences of acute respiratory tract infection (ARI) and acute lower respiratory infection (ALRI) were 6.1 and 0.5 per child-year, respectively, in children less than 5 years old in a depressed urban community in Manila. The peak age-specific incidence occurred in those children 6-23 months old for ARI and 6-11 months old for ALRI. Age less than 2 years, malnutrition, household crowding, and parental smoking were associated with a statistically significant, though modest, increase in ARI morbidity. The crude mortality rate was 14.3 per 1,000 children 0-4 years old, with a corresponding ARI-specific mortality rate of 8.9 per 1,000. The prevalence of viral infection was 32.8 and that of bacteremic ALRI was 6.7 per 1,000 children with moderate ALRI. Respiratory syncytial virus was the predominant viral pathogen, while Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus were the most frequently isolated bacterial pathogens. Transmission of respiratory pathogens in depressed communities, facilitated by inadequate housing, inaccessible health services, and prevalent malnutrition, will continue unless meaningful socioeconomic improvement is realized. 