A 7‑month‑old infant presents with two days of fever, rhinorrhea, cough, and vomiting; what is the most likely diagnosis and how should it be managed?

Viral Upper Respiratory Infection (Most Likely Diagnosis)

This 7-month-old infant most likely has a viral upper respiratory infection (URI), and management should focus on supportive care with antipyretics and fluids at home, while carefully monitoring for warning signs that would require medical evaluation.

Most Likely Diagnosis

The constellation of fever, rhinorrhea, cough, and vomiting for 2 days in a 7-month-old is classic for a viral URI, most commonly caused by respiratory syncytial virus (RSV), influenza, or other respiratory viruses that circulate during winter months 1, 2. In infants, influenza commonly presents with fever, cough, rhinorrhea, and gastrointestinal symptoms including vomiting and nausea 1. RSV is the leading cause of lower respiratory tract infections in children under one year and typically presents with fever, runny nose, and cough 2.

Initial Home Management

For mild symptoms without red flags, home management is appropriate:

• Antipyretics: Acetaminophen (never aspirin in children under 16 years due to Reye syndrome risk with influenza) 1
• Adequate hydration: Encourage fluids 1
• Nasal saline irrigation: Isotonic saline with nasal aspiration can reduce mucus, improve breathing, and lower the risk of complications like otitis media 3
• Supportive care: Most viral URIs resolve within 7 days, though cough may persist longer 1

Critical Red Flags Requiring Immediate Medical Evaluation

This infant must be assessed by a physician if any of the following develop:

High-Risk Features (Require GP or Emergency Assessment)

• Vomiting >24 hours (this infant is approaching this threshold at 2 days of illness) 1
• Breathing difficulties: Markedly raised respiratory rate, grunting, intercostal recession, nasal flaring 1
• Drowsiness or altered consciousness 1
• Signs of dehydration: Poor feeding, decreased urine output, dry mucous membranes 1
• Fever >38.5°C in an infant under 1 year warrants physician evaluation 1
• Signs of septicemia: Extreme pallor, hypotension, floppy infant 1

Influenza-Specific Concerns

• Febrile seizures occur in up to 20% of children hospitalized with influenza and are more likely to recur compared to other causes 4
• Secondary bacterial pneumonia: If fever persists or worsens after initial improvement, consider Streptococcus pneumoniae or Staphylococcus aureus superinfection 4
• Otitis media develops in approximately 25% of children under 5 with influenza 4

When to Consider Antiviral Therapy

Oseltamivir may be considered if:

• The infant has been symptomatic for <48 hours (ideally) 4
• However, infants under 1 year are at higher risk for severe complications and should be seen by a GP for assessment 1
• The benefit of oseltamivir is limited beyond 48 hours of symptom onset 4

When to Consider Antibiotics

Antibiotics are NOT indicated for uncomplicated viral URI. However, antibiotics should be considered if:

• Vomiting persists >24 hours with high fever (>38.5°C) and cough, suggesting increased risk of bacterial complications 1
• Signs of bacterial superinfection develop: new or worsening fever after initial improvement, severe earache, or respiratory distress 1
• Persistent symptoms >10 days without improvement suggest bacterial sinusitis (though less common at 7 months) 5, 6

Specific Management Algorithm for This Infant

Given this infant's current presentation (2 days of symptoms with vomiting):

1. If vomiting is resolving and infant is feeding well: Continue home management with antipyretics, fluids, and nasal saline 1, 3

2. If vomiting continues beyond 24 hours total OR infant develops any red flag: Immediate GP or emergency department evaluation 1

3. If fever >38.5°C: Physician assessment is warranted given age <1 year 1

4. Monitor closely for: Breathing difficulties, drowsiness, poor feeding, decreased urine output, or worsening symptoms 1

Common Pitfalls to Avoid

• Do not dismiss persistent vomiting in a febrile infant—this is a red flag requiring medical evaluation 1
• Do not use aspirin for fever control due to Reye syndrome risk with influenza 1
• Do not delay evaluation if the infant appears drowsy, has breathing difficulties, or shows signs of dehydration 1
• Do not prescribe antibiotics for uncomplicated viral URI without evidence of bacterial superinfection 1, 3
• Be aware that infants under 1 year have a lower threshold for complications and warrant closer monitoring or physician evaluation 1