An 11-month-old boy presented acutely with a 3-day history of fever, vomiting and diarrhoea. A background of recent gastroenteritis among family members was noted. On admission, the patient was lethargic, dehydrated and had tachypnoea; general examination was otherwise unremarkable.

A provisional diagnosis of viral gastroenteritis was made. However, the tachypnoea prompted …