Influenza and antiviral treatment: Case

This school-age child with asthma presents the classic severe-influenza trajectory: an abrupt febrile illness in a high-risk host, early viral pneumonia complicated by an asthma exacerbation, and then the feared biphasic deterioration of secondary bacterial pneumonia. The candidate must demonstrate risk-stratified antiviral use, escalation of respiratory support, empirical antibiotic selection for post-influenza bacterial pneumonia, and a prevention plan for the child and the household. [2]

Clinical findings

The key findings at presentation are the abrupt onset in a child with a high-risk condition, the hypoxia and intercostal recession of viral pneumonia, and the wheeze of an influenza-triggered asthma exacerbation. The candidate should identify that chronic lung disease places this child in a different risk stratum, in which the same virus is far more likely to cause pneumonia, respiratory failure and a complicated course. [2]

The examination should assess work of breathing, oxygenation, recession, air entry and wheeze, and should look for the complications that change management — dehydration, altered consciousness suggesting encephalopathy, tachycardia out of proportion to fever or poor perfusion suggesting myocarditis, and a new fever after improvement suggesting secondary bacterial pneumonia. The differential at presentation includes an influenza-triggered asthma exacerbation, primary viral pneumonia, other viral respiratory infections, and Mycoplasma pneumonia, but the abrupt onset with the classroom cluster and the hypoxia make influenza with viral pneumonia the leading diagnosis. [2]

Management

The child needs admission, oxygen and supportive respiratory care. Salbutamol and an oral corticosteroid address the asthma exacerbation, but the candidate should emphasise that early antiviral treatment is the decisive intervention. Oseltamivir should be started empirically — this is a hospitalised, high-risk child, so severity governs the decision to treat and the clock does not. Dose by weight and age for a five-day course. A nasopharyngeal swab for influenza PCR confirms the diagnosis but must not delay the first dose. [1]

The candidate should describe escalating respiratory support as the viral pneumonia demands: high-flow nasal cannula for moderate hypoxia and work of breathing, non-invasive ventilation for escalating respiratory failure, and mechanical ventilation in the intensive-care unit for the child who tires or develops respiratory failure. The intensive-care series during the 2009 pandemic showed that respiratory failure was the dominant reason for PICU admission in children with influenza. [4]

The day-three deterioration is the biphasic course of secondary bacterial pneumonia. The child who improves for a day or two and then spikes a new fever with worsening breathlessness, mottling and tachycardia has developed secondary bacterial pneumonia until proven otherwise, most often Staphylococcus aureus including methicillin-resistant strains, Streptococcus pneumoniae or Haemophilus influenzae. The candidate should add empirical intravenous antibiotics immediately — for example a third-generation cephalosporin with an anti-staphylococcal agent such as flucloxacillin or vancomycin where MRSA is prevalent or the child is critically ill — alongside ongoing supportive care and completion of the oseltamivir course. Recognising this biphasic course and treating it early is one of the few things that genuinely changes the outcome of severe influenza. [3]

Complications and follow-up

Influenza in a high-risk child carries the risk of respiratory failure from viral pneumonia, the lethal secondary bacterial pneumonia that drives much of influenza mortality, influenza-associated encephalopathy, myocarditis, and severe myositis or rhabdomyolysis. The candidate should state that children managed promptly with antivirals, respiratory support and timely antibiotics generally recover, but delayed presentation or a missed secondary bacterial pneumonia can be fatal. [3]

After recovery, this child needs close follow-up of his asthma, completion of the annual influenza vaccine programme (he should receive the inactivated vaccine each year, two doses in any season he receives it for the first time under nine years), and a household vaccination plan so that the people around him — and any future infant — are protected. The discharge encounter is also a prevention opportunity: the household should be offered vaccination, high-risk contacts considered for post-exposure prophylaxis, and the family given a clear safety-net for any recurrence of fever with respiratory distress. The clinical encounter does not end when the child improves; it ends when the contacts are protected and the family is vaccinated. [1]