In infants under three months, fever is more likely than in older children to signal a serious bacterial infection — urinary tract infection most often, and occasionally bacteraemia or meningitis — and these infants can look well early on. Infants under one month carry the highest risk.
Assessment should include urine, blood tests including inflammatory markers and a blood culture, and a low threshold for lumbar puncture, especially in the first month. A reported fever at home counts, even if the infant is afebrile in clinic. Parents should be told clearly how to return quickly if feeding falls or the baby becomes drowsy.
- Treat any fever of 38 °C or more in an infant under three months as needing assessment the same day.
- Test urine in every febrile young infant.
- Keep a low threshold for blood culture and lumbar puncture in the first month of life.
- Accept a parent-measured fever as real, even if the infant is afebrile on arrival.
Why it matters
Young infants with serious infection often look deceptively well at first.
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