West Nile virus (WNV) is a mosquito-borne virus which in majority of cases causes only self-limited disease.
Despite that, in minority of cases (\~0.5%) it can infect the brain and cause severe and even life-threatening disease (neuroinvasive disease).
Recent study has shown that up to 40% of WNV patients who develop neuroinvasive disease, have antibodies against Interferons (anti-Type I interferon autoantibodies), which neutralizes interferons, and could explain the development of severe disease.
The investigators therefore assume that early treatment with interferon beta (the type of interferon against which most patients do not have neutralizing antibodies) could prevent the development of severe neuroinvasive WNV disease.
Patients with clinical presentation suspected as compatible with WNV infection, with symptoms including elevated fever, headache or flaccid paralysis or fever with encephalopathy.
Positive anti-WNV IgM serology / WNV PCR from either serum, urine or CSF.
Patients older than 70 years of age, who are at higher risk for the presence of neutralizing anti-Type I IFN auto-antibodies, and therefore at higher risk for developing severe neuroinvasive disease. Only patients who fulfill the diagnostic criteria above will be included.
Patients presenting with neuroinvasive WNV disease, including either flaccid paralysis or encephalitis, independent of their age, excluding a presentation consistent with isolated aseptic meningitis (headache, fever, 6th nerve palsy). Only patients who fulfill the diagnostic criteria above will be included.
Patients younger than 18 years old.
Pregnant women.
Contraindication for the administration of the drug: Hypersensitivity to natural or recombinant interferon beta, and decompensated liver disease.
A patient with neuroinvasive disease showing consistent spontaneous improvement over a period of > 2 days and mRS of below 4.