West Nile Virus (WNV) disease is caused by a virus spread through mosquito bites. Most infected people are asymptomatic, but about 1 in 5 may experience fever, rash, and muscle aches. Rarely, it can cause serious brain and spinal cord inflammation and death. We present a case initially diagnosed as Motor Neurone Disease (MND) which ‘improved’ on follow-up and when investigated, was positive for WNV antibodies in serum.

A 48-year-old male presented with complaints of quadriparesis and slurring of speech. In February 2020 he started developing weakness of both lower limbs, which was insidious in onset and gradually progressive in nature, associated with wasting and twitching of muscles. Later, upper limbs weakness developed, manifesting as difficulty in gripping and lifting hands above shoulders. Patient also had slurred and incoherent speech with dysphagia. In November 2021 he was admitted to a teaching hospital in Delhi with a clinical diagnosis of MND.

On admission he had normal cognition, dysarthria, bilateral muscular atrophy (right worse), quadriparesis with hypotonia, hyperreflexia, mute plantars and no cerebellar sign. Nerve Conduction Studies and Electromyography was suggestive of preganglionic neurogenic involvement of bulbar, cervical and lumbosacral segments with evidence of ongoing denervation and chronic reinnervation changes. Riluzole was started and continued on follow up.

When seen in our OPD, family informed of ‘improvement’ in speech which surprised us. Myeloradiculitis due to WNV was suspected. Serum was positive for WNV IgG 98.5 RU/ml (>22 is positive) and WNV IgM 0.92 (borderline positive). Riluzole was stopped. Patient continued to improve with physiotherapy over 1 year of follow-up consultations. 

Human WNV infection is caused by bites from infected mosquitoes. We may consider WNV Myeloradiculitis in differential diagnosis of MND. WNV can be found in unexpected regions of the world (such as in this case - India) due to climate change.