Acute respiratory tract infection in children in Idikan Community, Ibadan, Nigeria: severity, risk factors, and frequency of occurrence. A longitudinal, community-based study of the epidemiology of acute respiratory tract infection (ARI) in children less than 5 years old was carried out in a community of low socioeconomic level in Ibadan, Nigeria. The annual incidence of ARI ranged from 6.1 to 8.1 episodes per child per year. The incidence was highest in the first 2 years of life and decreased with increasing age. The incidence was higher in boys than in girls. ARI occurred in all seasons of the year. The most common symptoms were cough, nasal discharge, and fever, while the most common signs referable to the respiratory tract were abnormal breathing sounds, tachypnea, and chest retraction. 