Diagnosis of west Nile virus encephalitis in an immunocompromised returned traveller.

Background: The unwell returned traveller can pose unique diagnostic dilemmas to treating clinicians. We present a case of West Nile virus infection presenting with gastrointestinal disturbance, further complicated by encephalitis, in a returned immunocompromised traveller. Case Presentation: A 63 year old woman with a past history of follicular lymphoma, hypogammaglobulinaemia and cyclical neutropaenia was admitted to hospital with a diarrhoeal illness immediately after returning to Australia from abroad. Travel history included cruise travel on the Danube River followed by several weeks' travel in South-eastern Europe including Serbia and Croatia with exposure to rural areas and mosquito bites, but no exposure to unpasteurised foods, animal or farm contacts. On Day 5 of her illness, the patient developed confusion, nominal aphasia and a slow affect. Brain computed tomography (CT) and magnetic resonance imaging (MRI) were unremarkable. Cerebrospinal fluid (CSF) analysis demonstrated a mildly raised protein and a mild lymphocytic pleocytosis. Empiric treatment for meningoencephalitis was commenced with aciclovir, piperacillin-tazobactam and ampicillin along with intravenous immunoglobulins (IVIg) to treat hypogammaglobulinaemia. The patient required intubation for mechanical ventilation on Day 10 following progressive neurological impairment with fluctuating conscious state and unco-ordinated motor responses. A second MRI demonstrated new changes affecting bilateral thalami, mesial temporal structures and the brainstem. Electroencephalography showed subclinical seizure activity, which was treated with phenytoin and levetiracetam. Investigations, including CSF bacterial cultures, nucleic acid amplification for enterovirus and herpes multiplex, cryptococcal antigen and treponemal serology, were negative. Diagnosis of flavivirus was considered due to exposure to an area with local outbreak, supported by suggestive MRI changes with bilateral thalamic and basal ganglia i