Define the fever
Rectal temperature ≥ 38.0 °C. Rectal is the standard in this age group; axillary and tympanic readings are not reliable enough to make these decisions.
A history of fever at home counts, even if the child is afebrile on arrival.
Under 28 days — no risk stratification
Every febrile neonate gets:
- Full septic work-up: blood culture, urine culture by catheter or suprapubic aspirate (never a bag specimen), and lumbar puncture
- Admission and empiric IV antibiotics: ampicillin plus either cefotaxime or gentamicin
- Add aciclovir if there are features suggesting HSV — vesicles, seizures, maternal genital lesions, ill appearance, raised transaminases, CSF pleocytosis
The reason is not caution for its own sake: neonates have poor localisation, the immature immune system, and the specific organisms of vertical transmission — group B streptococcus, E. coli, Listeria, and HSV.
Appearing well does not lower the risk enough to change management. This is the single most examined point in paediatric emergency medicine.
29–60 days
Risk stratification is permitted using validated criteria (Rochester, Philadelphia, Step-by-Step, or the AAP framework), combining:
- Well appearance
- Previously healthy, term, no antibiotics
- Normal urinalysis
- Normal inflammatory markers — procalcitonin and CRP now carry more weight than the white cell count
- No focal infection
Low-risk infants may be managed with a shorter course of investigation and observation, sometimes without lumbar puncture, according to local protocol. High-risk infants are treated as neonates.
3–36 months
The conjugate pneumococcal and Hib vaccines transformed this age group; occult bacteraemia is now rare in the fully immunised.
- Well-appearing, immunised, with a source → treat the source
- Without a source → urinalysis and urine culture is the highest-yield test, especially in girls under 24 months and uncircumcised boys under 12 months
- Chest radiograph if there are respiratory signs, hypoxia, or a very high white cell count
- Unimmunised or under-immunised children are managed more like the pre-vaccine era
Red flags at any age
Toxic appearance, poor perfusion, petechial or purpuric rash, bulging fontanelle, inconsolability, paradoxical irritability (worse when held), grunting, apnoea, hypothermia in a neonate, or a parent's report that the child is simply not themselves.
Petechiae below the nipple line in a febrile child means meningococcal disease until proven otherwise — antibiotics before imaging, before transfer, before anything else.
Do not forget
Kawasaki disease in fever lasting five days or more in a young child, and inflicted injury as a cause of unexplained presentation. Both are missed by working only through the infection differential.