CNS Infections

Abstract

Worldwide central nervous system (CNS) infections in human and animal populations differ with both the geographical location and the immune status of the host. Encephalitis is caused by viruses from many different taxonomic groups but most frequently occurs in rabies and insect-borne virus (arboviruses) infections. However, human herpes viruses cause a range of acute, subacute and long-term neurological diseases in both immunocompetent and immunocompromised individuals and are the most common cause of CNS infection in Western countries. Infection with the retroviruses human immunodeficiency virus type-1 (HIV1) and human T cell leukaemia virus type-1 (HTLV1) can lead to an immunodeficiency marked by depletion of CD4+ T cells and eventually, if untreated, to neurodegenerative diseases, either as a direct result of infection with these agents or due to secondary opportunistic infections. HIV dementia is increasing in prevalence with more people living due to antiviral therapy. Members of the negative-strand RNA viruses (Mononegavirales), including measles, henipaviruses and members of the Bunyaviridae family, cause encephalitis associated with particular regions worldwide. RNA positive-strand toga and alpha virus infections are generally associated with tropical climates, but due to climate changes affecting their insect hosts they are increasingly moving northwards. While not cause by viruses, prion diseases, also known as transmissible spongiform encephalopathies, are invariably fatal and present a major challenge as they are caused by a rogue host protein. While we are close to eradiation of infections such as poliovirus and measles virus, in the next 10 to 20 years new pathogens will emerge. Increasing knowledge of virus-host interactions and the resulting neuroimmunology will allow identification of novel targets to develop future therapies for CNS infection. This edition first published 2014