We describe a fatal case of proven enterovirus 71 meningoencephalitis complicating monoclonal anti-CD20 antibody therapy for non-Hodgkin's lymphoma. B-cell depletion, an effective treatment strategy in an expanding spectrum of hematological and inflammatory disorders, impairs neutralising antibody-mediated clearance of enterovirus. The global threat of emerging neurotropic viruses such as enterovirus 71 is heightened by an increasing pool of susceptible individuals in non-endemic regions.