Enterovirus A71 (EV-A71) is a member of the species Enterovirus A in the Picornaviridae family. It is a non-enveloped, positive-sense single-stranded RNA virus and one of the principal causative agents of hand-foot-and-mouth disease. While many infections are mild, the virus can also lead to severe neurological complications such as encephalitis, meningitis and acute flaccid paralysis.
Virology and clinical features
EV-A71 has a genome of approximately 7.4 kilobases encoding a polyprotein that is cleaved into structural and non-structural proteins. The virus replicates in epithelial cells of the oropharynx and gastrointestinal tract and is shed in throat secretions and stool. Transmission occurs via the fecal-oral route, respiratory droplets and contact with contaminated surfaces. After initial replication in lymphoid tissue, EV-A71 may spread to the central nervous system through the bloodstream or peripheral nerves. Infections often present as hand-foot-and-mouth disease, characterized by fever and vesicular lesions on the hands, feet and oral mucosa. Some strains produce herpangina, a febrile illness with vesicles in the posterior oropharynx. Severe complications include aseptic meningitis, encephalitis, polio-like limb weakness and cardiopulmonary failure, particularly in young children. Diagnosis relies on reverse transcription polymerase chain reaction detection of viral RNA from throat swabs, stool or cerebrospinal fluid. There is no specific antiviral therapy; treatment is supportive. A killed EV-A71 vaccine has been licensed in some Asian countries and provides protection against symptomatic disease. Preventive measures include good hygiene, isolation of ill individuals and monitoring of outbreaks.
Outbreaks and important observations
EV-A71 has caused repeated outbreaks of hand-foot-and-mouth disease and neurological disease, particularly in Asia. Major epidemics in Malaysia and Taiwan in 1997 and 1998 resulted in dozens of fatalities, prompting increased surveillance. Large outbreaks in China in 2008 and subsequent years led to millions of cases and hundreds of deaths, and EV-A71 became a notifiable disease in the country. Genetic studies have identified multiple genogroups that circulate cyclically and occasionally recombine with other enteroviruses. While most infections occur in children under five, severe cases in adults have also been reported. In recent years, a decrease in EV-A71 circulation in some regions has been observed following vaccination campaigns. Enterovirus A71 remains a significant public health concern due to its ability to cause widespread outbreaks and serious neurological disease. Continued surveillance, vaccination where available, and hygiene measures are essential to control its impact. Related Terms: Enterovirus D68, Echovirus 30, Human Rhinovirus A, Human Rhinovirus C, Human Parechovirus 1