One of the things I quickly realized as a new attending was that residents rarely struggled with the straightforward febrile infant.
The pathway cases? Easy.
But every few shifts, someone would present a child and then pause halfway through the plan:
“Well… my last attending did something completely different.”
That’s where this talk came from.
These are the febrile infant cases that live in the gray zone – the infants who technically fall outside pathways, have viral symptoms, are premature, are hypothermic, or have findings that make you wonder whether standard algorithms fully apply.
Below are 5 high-yield pearls from a recent talk I gave for the Canada Pediatric Emergency Medicine National CME Series. At the bottom of the post, I provide references so you can review the relevant studies.
The full lecture can be viewed on the HipPEMcrates YouTube channel and is embedded below for anyone interested in diving deeper into the evidence and clinical dilemmas surrounding these cases.
1. The “61–90 Day Old” Infant Still Has Meaningful Risk – But Mostly Not Meningitis
Many clinicians breathe a sigh of relief once an infant crosses 60 days.
And while the risk of invasive bacterial infection does decrease, it doesn’t disappear.
The important nuance:
- UTIs remain relatively common
- Bacteremia becomes much less common
- Bacterial meningitis becomes exceedingly rare in well-appearing infants
For many of these infants, urine testing remains the highest-yield first step.
2. Viral Symptoms Matter
Not all viruses are created equal.
One study suggests that infants with “mucosally restricted” viruses (RSV, influenza, coronavirus) have significantly lower rates of bacterial infection compared to viral-negative infants.
That doesn’t mean “virus positive = no workup.”
But it does support a more nuanced approach – especially in well-appearing infants around 2 months of age with clear viral syndromes and reliable follow-up.
3. A True Acute Otitis Media in a Young Infant May Actually Lower Your Concern for IBI
A study of afebrile infants under 3 months with clinician-diagnosed acute otitis media found:
- Zero cases of bacteremia
- Zero cases of bacterial meningitis
The challenge, of course, is deciding whether it’s actually AOM versus a red tympanic membrane from crying or viral illness.
In many of these infants, “watch and wait” may be more reasonable than reflexively starting antibiotics.
4. Hypothermia Is One of the Most Anxiety-Provoking Findings in the ER
The frustrating part?
There’s no universally agreed-upon threshold.
And studies have failed to identify a single temperature cutoff that reliably predicts serious bacterial infection.
Context matters:
- Age
- Prematurity
- Environmental exposure
- Feeding
- Clinical appearance
- Ability to normalize temperature
A well-appearing 5-day-old with mild temperature instability is very different from a lethargic 5-week-old who remains hypothermic despite warming.
5. Premature Infants Don’t Always Behave Like Their Chronologic Age
This is one of the hardest groups to manage.
Emerging evidence suggests:
- Younger preterm infants may carry higher IBI risk
- But standard febrile infant inflammatory marker algorithms still appear to perform well
In practice, many clinicians still maintain a lower threshold for testing in former preemies – especially early in their corrected age.
Pearl #1 References:
Prediction Rule to Identify Febrile Infants 61-90 Days at Low Risk for Invasive Bacterial Infections
Prevalence of Bacterial Infection in Febrile Infant 61-90 Days Old Compared With Younger Infants
Pearl #2 References:
Risk of Bacterial Infections in Febrile Infants 61 to 90 Days Old With Respiratory Viruses
Pearl #3 Reference:
Invasive Bacterial Infections in Afebrile Infants Diagnosed With Acute Otitis Media
Pearl #4 References:
Clinician Management Practices for Infants With Hypothermia in the Emergency Department
Temperature threshold in the screening of bacterial infections in young infants with hypothermia
Performance of Febrile Infant Decision Tools on Hypothermic Infants Evaluated for Infection
Predicting Serious Bacterial Infections Among Hypothermic Infants in the Emergency Department
Hypothermia: A Sign of Sepsis in Young Infants in the Emergency Department?
Pearl #5 References:
Following Birth Hospitalization: Invasive Bacterial Infections in Preterm Infants Aged 7-90 Days
Rate of Urinary Tract Infections, Bacteremia, and Meningitis in Preterm and Term Infants
Diagnostic Accuracy of Risk-Stratification Strategies for Premature Febrile Infants 8-60 Days Old
Dr. Joshua Belfer, MD, is a Pediatric Emergency Medicine physician at the Children’s Hospital of Philadelphia, and is the Founder and Editor-in-Chief of HipPEMcrates. He can be reached at HipPEMcrates@gmail.com.
