There is no evidence for persistent enterovirus infections in chronic medical conditions in humans

Enteroviruses, togeth er w ith the rhinoviruses, aphthoviruses, and the cardioviruses, belong to the family of Picomaviridae1 The genus enterovirus can be further divided into polio-, ECHO-, Coxsackie A and B-, and the enteroviruses 68 to 71.Enteroviruses are the p ro to ty p e of positive-strand RN A viruses since the genom e is similar to eukaryotic mRNA.A small virally encoded protein, Vpg, is covalently attached to the 5 'end and a poly(A) tail is present at the 3 'en d of the viral RNA.O nce the virus has entered the host cell, uncoating is com pleted and the viral RNA is released into the cytoplasm of the cell w here the RNA is directly translated into a p o ly p ro tein 1 of M r about 200 000.D irectly after infection, h o st cell protein synthesis is shut-off.Evidence for the m echanism of poliovirus shut-off points tow ards the inactivation of initiation com plex elF-4F, in which the cleavage of a cellular protein p220 b y the 2A protease is tho u g ht to be involved.2Virus progeny are released b y cell-Iysis which is induced b y the infection itself.The virus can subse quently spread throughout the b o d y until neutralising antibodies arise that stop further spreading and eliminate the virus.A t that point, virus cultures will becom e negative.The role of cellular im m unity seems to be of less im portance than that of antibody.This is consistent w ith an obligatory cell-lysis form ing part of the in vivo infectious cycle.Thus, chronic enterovirus infections are only know n to occur in patients w ith agammaglobuli-naemia3 or neonates, in w hom the immune system is still immature.4It is possible to isolate virus from such patients, even in the chronic stage of the infection.In normal health, enteroviral infection m ay follow a biphasic course, w ith a secondary viraemia w ith dissem ination of the infection to target organs such as heart, brain, pancreas, or muscle.5 'A u th o r to w hom correspondence should be addressed.A b b re v iatio n s used: DM , dermatomyositis; IBM, inclusion body myositis; IDC, idiopathic dilated cardiomyopathy; IDDM , idiopathic diabetes mellitus; ISH, in situ hybridisation; PM, polymyositis; PPS, post-polio syndrome; PVFS, post-viral fatigue syndrome.