Influenza and antiviral treatment: Viva

Branch 1: Recognising influenza and triaging severity

The candidate should recognise the classic picture of influenza in an older child: the abrupt onset — within hours of appearing well — of high fever, dry cough, sore throat, myalgia and marked fatigue, against a background of community influenza activity. The suddenness is the clue that distinguishes influenza from the gradual, predominantly coryzal common cold, and the classroom cluster raises the pre-test probability in season. ^[2]

The candidate should then triage severity and risk. This child is alert and cardiovascularly stable with acceptable oxygenation, placing him in the non-severe category, but the candidate must state explicitly the features that would escalate management: respiratory distress or hypoxia, dehydration or poor feeding, altered consciousness or seizures suggesting encephalopathy, tachycardia out of proportion to fever or poor perfusion suggesting myocarditis, and a biphasic deterioration suggesting secondary bacterial pneumonia. The candidate should also establish the host risk profile — age under two, chronic lung, cardiac or neurologic disease, immunocompromise, long-term aspirin — because high-risk status lowers the threshold to treat. ^[2]

The examiner will probe the atypical infant presentation. The candidate should explain that an infant under two may have no localising respiratory story at all: fever, poor feeding, irritability, lethargy, apnoea or a sepsis-like picture can be the whole illness, and that influenza belongs in the differential of the unwell infant alongside bronchiolitis, sepsis and urinary infection. A low threshold to test and treat in season is what prevents the catastrophic miss. ^[2]