The spotted traveller

A 23 year old university student comes to see you with a febrile illness and a rash. She has just returned from a 6 week holiday in South East Asia having visited Thailand, Vietnam, Hong Kong and the Philippines. Prior to going away she went to a travel clinic, was appropriately immunised and given malaria prophylaxis which she has taken assiduously. Her symptoms have been present for about 3 days and consist of severe retro-orbital headache, diffuse myalgias, fevers and chills, and anorexia. The rash appeared the day before on her trunk and is now beginning to involve her arms with a slight papular element. She also has conjunctival haemorrhages and is febrile with a temperature of 38.9 degrees C. A full blood count done urgently does not show any malaria parasites but does reveal a low platelet count of 85,000 x 10(6)/L.