Respiratory infection, diarrhea and fever are three common infections in underfive children; there are substantial differences in the reported prevalence and ranking of these three morbidities between studies and surveys. Seasonal and year to year variation in prevalence of morbidity and impact of health care on the duration and severity of infection has not been explored. A large scale mixed longitudinal study of under-five children from urban low income households was carried out to document year to year and seasonal variations in the prevalence and type of morbidity and utilization of health care for morbidity and their impact on duration and severity of morbidity. Between January 2012 and Dec 2015 a total of 3888 pre-school children were investigated and 74636 observations were made; prevalence of morbidity was 10.3% (range 7.2%-11.6%). Prevalence of morbidity was higher between July and October. Respiratory infection was the most common and diarrhea was the least common illness in children. Over years there was a rise in the respiratory illness because of increase in construction activity in the study area. There was a fall in diarrhoeal diseases after construction of water supply and drainage system. Majority of the households accessed health care; as a result duration of illness was short and severe morbidity was rare. Improvement in environmental hygiene can result in reduction in morbidity. Access to health care reduces duration and severity of infection.