Enterovirus 71 (EV71), first isolated in California in 1969, is a member of human enterovirus species A, belongs to genus Enterovirus, family Picornaviridae. It is a small non-enveloped virus with viral particle size about 30 nm in diameter. Infections of enterovirus 71 / EV71 occur mainly in children, and commonly result in mild and self-limiting hand, foot, and mouth disease (HFMD).
However, severe neurological complications such as poliolike paralysis, aseptic meningitis, and encephalitis may be caused by enterovirus 71 / EV71 acute infections in young children, especially those less than 5 years old. This virus is transmitted through the fecal-oral route, and it is largely replicated in the tonsils and intestinal lymphoid tissue. Thus, the spread of the virus from a patient's gastrointestinal tract can last for several weeks. It is also possible that enterovirus 71 / EV71 may reach the central nervous system (CNS) by penetrating the blood-brain barrier somehow or by a neuronal route. During the past five decades, there have been a number of enterovirus 71 / EV71 outbreaks worldwide, though countries in Asia-Pacific area are seriously affected in the last twenty years. Since no effective vaccine or approve antiviral agents has been developed, enterovirus 71 / EV71 becomes an important and emerging threat to public health.