2.4 Patients Patients aged 1 month to 16 years with an acute illness for a maximum of 5 days are included consecutively. Children are excluded if the acute episode was caused by a merely traumatic or neurological illness, intoxication, psychiatric or behavioural problem without somatic cause, or an exacerbation of a known chronic condition. If a physician includes children twice in the study within 5 days, the second registration is considered a repeated measurement on the same subject and is subsequently excluded from the analysis.