Tada et al in 2004 identified clinically mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) as a new type of acute encephalopathy, characterized by transient splenial lesions with high-signal intensity on diffusion-weighted magnetic resonance imaging (MRI), a mild clinical course, and a good outcome. MERS has been associated with various infectious diseases including influenza A and B (the most common pathogens), following by mumps virus, adenovirus, rotavirus, streptococci, and E.coli.