Evidence for enteroviral persistence in humans

This study presents the first molecular evidence for enteroviral persistence in humans by analyzing serum samples from eight chronic fatigue syndrome (CFS) patients. Researchers used PCR to detect enteroviral sequences in blood samples taken at least 5 months apart (up to 24 months) and compared the nucleotide sequences of the 5' non-translated region. Four patients had highly similar sequences (≥97.5% identity) that retained unique shared patterns across time points, indicating viral persistence. One patient showed evidence of infection with two different enteroviruses. Three others showed greater sequence divergence suggesting re-infection rather than persistence. Most sequences clustered with Coxsackie B-like viruses and differed from known enterovirus types. The researchers observed that enteroviral RNA polymerase error rates allow gradual sequence divergence during replication while maintaining viability constraints. Patient symptoms remained essentially unchanged over the sampling period regardless of persistence versus re-infection status. The exact body sites where viruses persist remain undetermined.

Key findings

• Four of eight CFS patients showed enteroviral sequence persistence in blood samples up to 24 months apart with ≥97.5% nucleotide similarity and unique shared sequence patterns
• The persistent enteroviral sequences represent atypical strains related to Coxsackie B viruses, distinct from known enterovirus types
• One patient demonstrated infection with two genetically distinct enteroviruses, while others showed evidence of re-infection with related strains
• Enteroviral sequences from CFS patients form a closely related genetic subgroup that differs from standard enterovirus classifications
• Clinical symptoms in CFS patients remained unchanged regardless of whether enteroviral persistence or re-infection occurred