Human Parechovirus Infection, Denmark

Thea K. Fischer

, Sofie Midgley, Camilla Dalgaard, and Alex Y. Nielsen

Author affiliations: Statens Serum Institut, Copenhagen, Denmark

Abstract

Human parechoviruses (HPeVs) often cause severe illness among young children. National surveillance with routine testing of all cerebrospinal fluid, fecal, and tissue samples was conducted during January 2009–December 2012 in all counties in Denmark (6,817 samples from 4,804 children were screened for HPeV). We detected HPeV RNA in 202 (3.0%) specimens from 149 persons. Young infants were at highest risk for HPeV, and 9 (6%) of the HPeV-infected children died, probably of their HPeV illness. HPeV3 was the most common genotype identified, and 5 closely related clades of HPeV3 circulated in Denmark throughout the study period. Our study adds perspective on the prevalence and clinical and molecular virologic characteristics of HPeV infection.

Human parechoviruses (HPeVs) have recently been recognized to cause a variety of symptoms ranging from mild diarrhea to sepsis and meningitis, particularly among young children. HPeVs belong to a large family of nonenveloped, positive-sense, single-stranded RNA viruses, thePicornaviridae, which comprises 12 genera (and 5 proposed genera). Six genera are associated with human infections: cardiovirus (saffold virus), cosavirus, enterovirus (EV), hepatovirus (hepatitis A), kobuvirus (Aichi virus) and HPeV. HPeV1 and HPeV2, originally known as echovirus 22 and 23 of the EV genus, respectively, were reclassified in 1999 as a separate genus (Parechovirus) on the basis of genetic and biologic differences (1). Since the reclassification, the number of known HPeVs has increased and now totals 16 genotypes (www.picornaviridae.com/parechovirus/hpev/hpev.htm).

HPeV1 is known to be associated with asymptomatic infection. HPeV3 seems to be more or less well established (2–4). The remaining known HPeVs are clinically unexplored.

Whereas HPeV3 has been reported to be associated with sepsis-like syndrome, meningitis, encephalitis, and hepatitis in neonates and young infants (2), most HPeV infections are asymptomatic or associated with mild respiratory and/or gastrointestinal symptoms (4). HPeV incidence has been reported to show a seasonal pattern in temperate climates, with different types cocirculating simultaneously (5). Although HPeV infections are relatively common in most settings, experience from long-term population surveillance is somewhat sparse. We used 4 years of national laboratory surveillance to describe the molecular epidemiology of HPeV, including phylogenetic characteristics of the emerging HPeV epidemic, in Denmark.