Murray Valley encephalitis virus (MVEV) is a mosquito‐borne virus that is found across Australia, Papua New Guinea and Irian Jaya. MVEV is endemic to northern Australia and causes occasional outbreaks across south‐eastern Australia. 2011 saw a dramatic increase in MVEV activity in endemic regions and the re‐emergence of MVEV in south‐eastern Australia. This followed significant regional flooding and increased numbers of the main mosquito vector, Culex annulirostris, and was evident from the widespread seroconversion of sentinel chickens, fatalities among horses and several cases in humans, resulting in at least three deaths. The last major outbreak in Australia was in 1974, during which 58 cases were identified and the mortality rate was about 20%. With the potential for a further outbreak of MVEV in the 2011–2012 summer and following autumn, we highlight the importance of this disease, its clinical characteristics and radiological and laboratory features. We present a suspected but unproven case of MVEV infection to illustrate some of the challenges in clinical management. It remains difficult to establish an early diagnosis of MVEV infection, and there is a lack of proven therapeutic options.

titres. Our patient meets the 2015 Consensus Diagnostic Criteria for NMOSD. 1 Treatment with high dose corticosteroids and rituximab lead to clinical and radiological improvement, but she had a clinical relapse 10 months later with new LETM (T3-T7), necessitating increased immunosuppression with more rigorous rituximab dosing of 1000mg every 6 months. Conclusions Double positivity for both Aquaporin-4 and MOG antibodies in NMOSD is rare. We describe a case of doublepositive NMOSD occurring following an infective illness. This case demonstrates that NMOSD may occasionally masquerade as post-infectious Acute Disseminated Encephalomyelitis and highlights the importance of checking antibodies in these patients, given the treatment strategies and risk of relapse differs considerably.