Children aged 2 months to 2 years admitted to hospital will be considered for inclusion and enrolment stratified by nutritional status. Following informed consent, baseline data of prognostic importance, including demographic and social information, a detailed clinical examination, anthropometry and measurement of vital signs, including pulse oximetry, will be collected using a standard proforma. A research blood sample will be collected together with the routine clinical blood draw to minimize the patient's discomfort. Rectal swabs and faecal sample will also be obtained from all children.