Enterovirus infections with special reference to enterovirus 71.

The enteroviruses comprise a large group of immunologically distinct serotypes of viruses belonging to the family of Picornaviridae. Many enteroviruses cause diseases in human, but the infections are generally mild as asymptomatic, therefore, enteroviruses are considered to be unimportant as human pathogens. However, enteroviruses may also result in serious or even fatal disease (as shown in the enterovirus 71 (EV71) epidemic in Taiwan in 1998). There are three types of polioviruses, Coxsackievirus group A and group B viruses, and echoviruses group. All together a total of 67 types are available. Starting from enterovirus type 68 to 71, they are named as enterovirus types. Enterovirus type 72 is hepatitis A virus. Paralytic disease of poliomyelitis was recorded in ancient time but characterization of poliovirus was not reported until the turn of the 19th century that poliomyelitis was a viral disease. The major breakthrough for diagnosing and controlling of poliomyelitis was the discovery that poliovirus can be propagated in human embryonic tissues in cultures. As soon as cultures of human and monkey cells began to use for isolating polioviruses in stool specimen of patients, more unknown viruses were isolated which unlike polioviruses nor Coxsackie viruses; they were called "orphan" viruses or human enteric viruses, name later simplified to "echoviruses". Morphologically all enteroviruses are alike. They are small, ether insensitive viruses with an RNA genome. Their nucleic acid is single stranded, and the nucleocapsid has a cubic (icosahedral) symmetry, and is naked. The host ranges of enteroviruses vary greatly from one type to the next and even among strains of the same type. Polioviruses have a very restricted host range among laboratory animals. Virus isolation is the best method for diagnosis of enterovirus infection, but infection in the central nervous system (CNS) may be detected by polymerase chain reaction (PCR). Currently final identification and serotyping of enteroviruses are by indirect immunofluorescent tests using monoclonal antibody or by neutralization test using antiserum pools described by Lim and Benyesh-Melnick. The incidence and prevalence of diseases associated with the enterovirus infections are varied. The circulation of enteroviruses recently in Tainan and the epidemic of EV71 in Taiwan in 1998 are described in this review. Although poliovirus infection may be eradicated from the world due to the efficient vaccination program, there is no specific antiviral agents for either treatment or prevention for other enterovirus infections. In 1991, a new antiviral "pleconaril" which is a novel orally bioavailable and systematically acting small molecule inhibitor for picornaviruses. "Pleconaril" is currently in clinical trials for treatment of enterovirus meningitis and respiratory infections.