Enteroviruses: Enterovirus 71
Ooi MG, Solomon T
Although poliomyelitis has been eradicated from much of the globe, during the past 15 years countries in the Asia-Pacific region have been afflicted by large outbreaks of infection with the related human enterovirus A71 (EV71). This infection affects mostly children, causing hand-foot-and-mouth disease, aseptic meningitis, poliomyelitis-like acute flaccid paralysis, brainstem encephalitis, and other severe systemic manifestations, particularly pulmonary edema and cardiorespiratory collapse. Being an RNA virus, EV71 lacks a proofreading mechanism and is evolving rapidly, with new outbreaks occurring across Asia in regular cycles. The subgenogroups appear to differ in their clinical epidemiological properties, with some of the more recently evolved subgenogroups having potential to cause explosive outbreaks. There is controversy over the pathogenesis of the severe cardiopulmonary manifestations and the relative contributions of neurogenic pulmonary edema, cardiac dysfunction, increased vascular permeability, and “cytokine storm.” Clinical predictors of the development of severe disease include high temperature and lethargy, and a lumbar puncture may reveal pleocytosis. Of the many alternative biological samples and laboratory tests with diagnostic utility, PCR applied to swabs from the throat or vesicle fluid, if available, is one of the most efficient. Magnetic resonance imaging reveals features of inflammation, particularly in the anterior horns of the spinal cord, the dorsal pons, and the medulla. There is no established antiviral treatment. Although untested in formal trials, intravenous immunoglobulin appears to be beneficial in severe disease, perhaps through nonspecific anti-inflammatory mechanisms. Milrinone appears helpful in treatment of cardiac dysfunction. To control outbreaks, social distancing (e.g., closing nurseries) has been attempted as a public health measure, but its effectiveness has not been fully examined. An inactivated whole virus vaccine has been found to be safe and effective in a phase 3 randomized double-blind placebo-controlled trial.
Viral Infections of Humans: Epidemiology and Control