Influenza and antiviral treatment: SAQ

This infant presents the archetypal paediatric influenza scenario: an unwell infant in influenza season with an affected household contact, atypical respiratory distress rather than the classic abrupt febrile illness of an older child, and then the feared biphasic deterioration that signals secondary bacterial pneumonia. Recognising both phases — the early empiric antiviral window and the later septic deterioration — is what the question tests. [2]

Question 1 (10 marks)

Outline your initial assessment, investigations and the rationale for early oseltamivir in this infant. [2]

Begin with a structured airway, breathing and circulation assessment. This infant is in respiratory distress with intercostal recession and an oxygen saturation of 91 percent in air, so he needs immediate oxygen, continuous monitoring and a low threshold for escalation. Measure a full set of vital signs including temperature, respiratory rate, heart rate, blood pressure and capillary refill, and weigh him for drug dosing. Assess feeding tolerance, hydration and urine output, and examine for the complications that change disposition — dehydration, altered conscious state, and the tachycardia and poor perfusion of myocarditis. [2]

The history is itself diagnostic. The mid-winter presentation, the household contact with confirmed influenza, and the infant's fever with poor feeding and respiratory distress make influenza the leading working diagnosis. In an infant, influenza may present without the classic cough-and-myalgia story of an older child; fever, poor feeding, irritability, lethargy or apnoea, and a sepsis-like picture can be the whole illness, and influenza belongs in the differential of the unwell infant alongside bronchiolitis, sepsis and urinary infection. [2]

Send a nasopharyngeal aspirate or flocked swab for influenza PCR, ideally as part of a respiratory-virus panel. A full blood count, electrolytes, C-reactive protein and blood cultures are reasonable in a sick infant to stage severity and to detect bacterial co-infection, and a chest X-ray is indicated given the respiratory distress and hypoxia. The key principle is that a sick child should never wait for the PCR result before starting antivirals — a positive test later only confirms what the severity demanded up front. [2]

Start oseltamivir empirically. The landmark treatment trial established that oseltamivir shortened illness and reduced acute otitis media in children, and pharmacokinetic work established safe, effective age-specific dosing for infants and neonates under two years. Severity, not the clock, drives treatment in the hospitalised child, and this infant — under two, hypoxic and unwell — meets every criterion for early empiric antiviral therapy. Dose by weight and age for a five-day course, and place the child under droplet precautions throughout the admission. [1]