Key points
- Fever: 38.0 °C (100.4 °F) or higher; the guideline covers well-appearing term infants 8–60 days old.
- Abnormal inflammatory markers: procalcitonin above 0.5 ng/mL, CRP above 20 mg/L, ANC above 4,000/µL; temperature above 38.5 °C counts if procalcitonin is unavailable.
- 8–21 days: urine, blood culture and LP for all; IV antibiotics and admission.
- 22–28 days: urine, blood culture and markers; LP if any marker is abnormal; some low-risk infants can be observed without antibiotics.
- 29–60 days with normal markers and urine: no LP and no antibiotics, with follow-up within 24 hours.
- Urine culture: catheter or suprapubic aspirate only.
- Suspected HSV: send CSF and blood PCR, surface swabs and liver tests, and start acyclovir 20 mg/kg IV every 8 hours.
Who the guideline covers
The AAP 2021 guideline applies to well-appearing, full-term infants (37 weeks or more) aged 8–60 days with a temperature of 38.0 °C (100.4 °F) or higher at home or in the clinic.
Ill-appearing infants are outside the risk stratification: they get a full sepsis evaluation, broad IV antimicrobials and admission.
- Excluded: preterm infants, infants in the first week of life, chronic illness or immune problems, a focal bacterial infection (such as cellulitis or osteomyelitis), and recent antibiotics or vaccines.
- An infant with bronchiolitis or another clear viral illness may still have a UTI; the guideline does not apply to clinical bronchiolitis.
- Measure fever rectally when possible; a reliable caregiver report of fever counts.
Tests and the inflammatory marker cut-offs
- Urinalysis for all. Send the urine culture from a catheter or suprapubic aspirate; bag urine is not used for culture.
- Blood culture for infants 8–28 days old, and in older infants when markers are abnormal or antibiotics are planned.
- Inflammatory markers (IMs): procalcitonin above 0.5 ng/mL, CRP above 20 mg/L, or ANC above 4,000/µL (some studies use 5,200/µL). Any one abnormal value is abnormal.
- If procalcitonin is unavailable, a temperature above 38.5 °C (101.3 °F) is an extra abnormal marker.
- CSF studies: cell count, glucose, protein, Gram stain and bacterial culture; add enterovirus or HSV PCR when indicated.
- CSF pleocytosis in the guideline: about 15 or more WBC/µL in infants 8–28 days old and 10 or more in infants 29–60 days old.
Management by age group
A positive urinalysis in a 29–60-day-old with normal markers carries a very low risk of meningitis, so the guideline does not require an LP.
| Age | Tests | Treatment and disposition |
|---|---|---|
| 8–21 days | Urinalysis and urine culture, blood culture, LP for all; IMs may be sent | IV antibiotics and admission for all |
| 22–28 days, any IM abnormal | Urine, blood culture, IMs and LP | IV antibiotics and admission |
| 22–28 days, IMs normal | Urine, blood culture, IMs; LP may be done | Normal UA and normal CSF: home observation with recheck within 24 hours is possible. No LP done: observe in hospital (with or without antibiotics) |
| 29–60 days, IMs normal, UA negative | Urine, blood culture optional, IMs; no LP | No antibiotics; home with follow-up within 24 hours |
| 29–60 days, IMs normal, UA positive | Urine culture; no LP | Oral antibiotics for presumed UTI at home; recheck within 24 hours |
| 29–60 days, any IM abnormal | Blood culture; LP may be done | Ceftriaxone; admit, or home if CSF is normal (or not obtained in selected cases) and a 24-hour recheck is assured |
Empiric antibiotics and doses
- Gentamicin 4 mg/kg IV every 24 hours; ceftazidime and cefepime 50 mg/kg per dose (150 mg/kg/day divided every 8 hours).
- Ceftriaxone 100 mg/kg/day for meningitis is a daily total: once daily, or 50 mg/kg per dose every 12 hours.
- Vancomycin 60 mg/kg/day divided every 6–8 hours: every 8 hours means 20 mg/kg per dose.
- Ill-appearing infants get broad coverage, typically ampicillin plus a cephalosporin with gram-negative coverage, vancomycin, and acyclovir.
- Ceftriaxone is avoided in the first weeks of life when the infant has hyperbilirubinemia or needs IV calcium.
| Situation | Empiric therapy |
|---|---|
| 8–21 days, no meningitis | Ampicillin plus gentamicin or ceftazidime (or cefepime) |
| 22–28 days, no meningitis | Ceftriaxone, or ampicillin plus gentamicin or ceftazidime |
| 29–60 days, no meningitis | Ceftriaxone 50 mg/kg IV or IM every 24 hours |
| 29–60 days, UTI with normal IMs | Oral cephalosporin such as cephalexin; ceftriaxone 50 mg/kg IV or IM if a first parenteral dose is needed |
| Suspected meningitis, 0–28 days | Ampicillin plus ceftazidime or cefepime (meningitic doses); add acyclovir if HSV is possible |
| Suspected meningitis, 29–60 days | Ceftriaxone 100 mg/kg/day plus vancomycin; add acyclovir if HSV is possible |
Neonatal herpes simplex virus (HSV)
Neonatal HSV is most common in the first 3 weeks of life, and many infants have no skin lesions at presentation. Think of it in any young infant who fits the clues below.
- Bedside clues: vesicles or mucosal ulcers, seizures, hypothermia, or a sepsis-like illness; maternal genital HSV lesions or fever around delivery.
- Laboratory clues: CSF pleocytosis with a negative Gram stain, raised aminotransferases (ALT), leukopenia or thrombocytopenia.
- Send: CSF HSV PCR, blood HSV PCR, surface swabs (mouth, nasopharynx, conjunctivae, rectum and any vesicles) and liver tests.
- Start IV acyclovir 20 mg/kg per dose every 8 hours (term infant, normal kidney function) while results are pending.
Common questions
Does every febrile infant under 60 days need a lumbar puncture?
No. Under the AAP 2021 guideline, LP is done for all infants 8–21 days old, for 22–28-day-olds with an abnormal inflammatory marker, and is optional in 29–60-day-olds with abnormal markers. Well-appearing 29–60-day-olds with normal markers do not need one.
What procalcitonin level is abnormal in a febrile infant?
Procalcitonin above 0.5 ng/mL. CRP above 20 mg/L and ANC above 4,000/µL are the other abnormal markers in the guideline.
What temperature is a fever in a young infant?
38.0 °C (100.4 °F) or higher, ideally measured rectally.
Study this topic
Sources
- AAP 2021: Evaluation and management of well-appearing febrile infants 8 to 60 days old (Pediatrics)
- AAP Red Book: Herpes simplex (neonatal HSV evaluation and treatment)
Written for Pedemy in our own words from the sources above; checked November 2026. For education only, not medical advice; check doses and local protocols before treating a patient. Pedemy is independent and not affiliated with or endorsed by the organizations cited.