Fever and rash in a returning traveller

A previously fit and well 26 year old male student of Chinese origin attended the emergency department with a five day history of a febrile illness. He had returned to the United Kingdom from a three week visit to Malaysia and Singapore the day before the illness began. His main symptoms were fever, headache, and nausea. He had also noted a faint widespread rash the day before admission.

On examination his temperature was 39.7°C, his blood pressure was 134/77 mm Hg, and he had a regular heart rate of 75 beats/min. He had a respiratory rate of 14 breaths/min and oxygen saturations of 98% on room air. The only relevant clinical finding was a confluent erythematous macular rash across his chest, back, arms, and legs, with multiple small discrete areas of sparing.

Full blood count showed haemoglobin 163 g/L (120-180), platelets 86×10⁹/L (130-400×10⁹), white cell count (WCC) 3.4×10⁹/L (4.5-11.0×10⁹), neutrophils 1.7×10⁹/L (2.0-7.5×10⁹; 40-75% WCC), lymphocytes 1.4×10⁹/L (1.3-3.5×10⁹; 20-45% WCC), and no eosinophilia (0.04-0.44×10⁹/L; 1-6% WCC). A blood film was negative for malaria parasites and confirmed thrombocytopenia with atypical lymphocytes. Renal function, liver function, and clotting tests were unremarkable and C reactive protein was less than 4 mg/L.