In a 2‑month‑old infant with a brief resolved fever, cough, normal respiratory rate, clear lungs, and good feeding, what is the most likely diagnosis and appropriate management?

Management of a 2-Month-Old with Cough and Resolved Fever

This well-appearing 2-month-old infant with a brief resolved fever, cough, clear lungs, normal respiratory rate, and good feeding most likely has a viral upper respiratory infection (bronchiolitis) and does not require chest radiography, but does require urinalysis to exclude urinary tract infection given the age and fever history. 1

Most Likely Diagnosis

Viral bronchiolitis is the most probable diagnosis in this clinical scenario. 2

• Respiratory syncytial virus (RSV) and other respiratory viruses commonly cause nasal congestion, rhinorrhea, mild fever, and cough in infants under 2 years, with symptoms typically worsening over several days before resolving. 2
• The brief fever (one day only) followed by resolution, combined with continued good feeding and normal respiratory rate, strongly suggests a self-limited viral process. 2
• The clear chest examination and normal respiratory rate argue against pneumonia or significant lower respiratory tract disease. 1

Critical Management Algorithm

Step 1: Confirm This Infant Does NOT Need Chest Radiography

Do not obtain a chest radiograph in this infant. 1

• Chest radiography is indicated only when specific clinical predictors are present: cough with hypoxia, rales on examination, high fever (≥39°C), fever duration >48 hours, or tachycardia and tachypnea out of proportion to fever. 1
• This infant has none of these predictors—the chest is clear, respiratory rate is normal, and fever lasted only one day. 1
• In febrile infants <60 days with no respiratory symptoms, the rate of positive chest radiographs is essentially zero (0% in one study of 36 infants). 3
• Obtaining unnecessary chest radiographs exposes infants to radiation and increases healthcare costs without clinical benefit. 3

Step 2: MUST Obtain Urinalysis and Urine Culture

You must obtain a catheterized urine specimen for urinalysis and culture despite the apparent benign presentation. 4, 5, 6

• Urinary tract infection accounts for >90% of serious bacterial infections in febrile children aged 2 months to 2 years. 4, 6
• At 2 months of age, this infant remains in a higher-risk category where fever—even if brief—warrants UTI screening. 5, 6
• Risk factors present in this case include young age (2 months) and documented fever, even though it resolved. 4, 6
• Never use bag collection—catheterization is mandatory due to contamination rates of 26% with bag specimens versus 12% with catheterization. 4, 6
• UTI in this age group carries serious consequences: 75% of febrile UTIs represent pyelonephritis, with 27-64% risk of renal scarring leading to kidney failure and hypertension later in life. 6

Step 3: Determine Need for Additional Laboratory Testing

Blood culture and complete blood count are reasonable given the age (2 months) and recent fever, even though the infant appears well. 5, 6

• At 2 months (60 days), this infant falls in the 29-90 day age range where risk stratification is appropriate but laboratory evaluation is often still warranted. 5
• Clinical appearance alone is unreliable: only 58% of infants with bacteremia or bacterial meningitis appear clinically ill. 6
• However, if the fever was truly brief (one day only) and the infant remains well-appearing with good feeding, some clinicians may defer blood work pending urine results. 5

Lumbar puncture is NOT indicated in this well-appearing infant without signs of meningismus, altered consciousness, or toxic appearance. 4

Step 4: Consider Viral Testing

RSV and influenza testing may be considered but are not mandatory in this scenario. 3

• In febrile infants <60 days with no respiratory symptoms and no sick contacts, RSV positivity is 0% and influenza positivity is approximately 2%. 3
• However, this infant does have a cough (a respiratory symptom), which slightly increases the yield of viral testing. 3
• A positive viral test does NOT exclude concurrent bacterial infection—viral and bacterial infections can coexist. 6
• The primary value of viral testing is potentially reducing the need for more invasive studies if positive, but this should not replace mandatory urine testing. 7

Disposition and Follow-Up

Close outpatient follow-up within 24 hours is mandatory if the infant is discharged home. 4, 5

• Ensure reliable communication between family and providers with access to emergency medical care. 4
• Do not discharge without confirming parental ability to judge clinical changes and return immediately if needed. 4
• Instruct parents to return immediately for: altered consciousness or severe lethargy, respiratory distress, signs of dehydration, persistent vomiting, petechial or purpuric rash, or fever persisting ≥5 days. 4

Common Pitfalls to Avoid

Do not assume the resolved fever eliminates concern for serious bacterial infection. 6

• Recent antipyretic use or natural fever resolution can mask infection severity and does not rule out serious bacterial infection. 6
• Home thermometer readings may be inaccurate—document rectal temperature in the clinical setting to confirm true fever history. 6

Do not skip urine testing because the infant "looks good." 4, 6

• Well appearance is falsely reassuring in this age group—UTI screening is non-negotiable at 2 months with fever history. 4, 6

Do not obtain chest radiography based on cough alone. 1

• Cough without other respiratory signs (tachypnea, hypoxia, rales) does not warrant chest radiography. 1
• Overuse of chest radiography leads to overdiagnosis and unnecessary radiation exposure. 4