Study design. Infants are enrolled at birth and followed until one year of age. Baseline data, cord blood and a maternal blood sample are collected at birth. Data on health and development are collected at scheduled visits at 2, 4, 6, 9 and 12 months of age (in HCMC there are two additional appointments at 1 and 3 months). A one ml blood sample is also collected at the visits at 4, 9 and 12 months. Families are asked to bring the infant to a study clinic with any illness. Clinical data are recorded on examination, and specimens are collected according to the symptoms and presumptive diagnosis. Detailed clinical data are collected daily for any infant admitted to hospital with an infectious disease. The four syndromes on which research studies are focused are febrile illness, acute respiratory infection, acute diarrhoeal disease, and hand foot and mouth disease, and the pathogens for which diagnostics are currently being performed are indicated.