Enteroviruses and Parechoviruses: Echoviruses, Coxsackieviruses, and Others

Enteroviruses and parechoviruses (family Picornaviridae) are ubiquitous human pathogens, causing a wide range of clinical presentations. These include asymptomatic infection, mild illness such as common colds and non-specific febrile illness, exanthems, hand, foot, and mouth disease, herpangina, conjunctivitis, and severe illness such as aseptic meningitis, encephalitis, neonatal sepsis, myocarditis, acute flaccid limb weakness or paralysis without spinal cord involvement, and acute flaccid myelitis. While over 100 enterovirus types have been identified in humans and animals, traditionally identified by antigenic tests but more recently according to genome sequence criteria, many more are being discovered and others are being reclassified. In this chapter, the focus will be on non-polio enteroviruses and parechoviruses that affect humans only. Parechoviruses were formerly classified as enteroviruses but now constitute their own genus; however, their spectrum of clinical disease manifestations is similar to that of enteroviruses. Both enteroviruses and parechoviruses are transmitted primarily through fecal-oral and respiratory routes and have a distinct seasonality in temperate climates.