Norovirus

Abstract

Norovirus, an RNA virus of the family Caliciviridae, is a human enteric pathogen that causes substantial morbidity across both health care and community settings. Several factors enhance the transmissibility of norovirus, including the small inoculum required to produce infection (<100 viral particles), prolonged viral shedding, and its ability to survive in the environment. In this review, we describe the basic virology and immunology of noroviruses, the clinical disease resulting from infection and its diagnosis and management, as well as host and pathogen factors that complicate vaccine development. Additionally, we discuss overall epidemiology, infection control strategies, and global reporting efforts aimed at controlling this worldwide cause of acute gastroenteritis. Prompt implementation of infection control measures remains the mainstay of norovirus outbreak management.

FIG 1

Immunoelectron microscopy identifies a 27-nm particle associated with acute infectious nonbacterial gastroenteritis. Shown is an aggregate observed after incubation of a second-passage stool filtrate from the original Norwalk outbreak with a 1:10 dilution of postchallenge antiserum of an experimentally infected volunteer. These particles are heavily coated with antibody. (Adapted from reference with permission.)

FIG 2

The human norovirus genome. The genome is comprised of a linear, positive-sense RNA, ∼7.6 kb in length, covalently linked to the viral protein genome (VPg) (solid black circle) at the 5′ end and polyadenylated at the 3′ end. There are three open reading frames (ORFs), designated ORF-1, ORF-2, and ORF-3, encoding 8 viral proteins. ORF-1 encodes the 6 nonstructural (NS) proteins that are proteolytically processed by the virally encoded cysteine proteinase (Pro). ORF-2 and ORF-3 encode the structural components of the virion, viral protein 1 (VP1) and VP2, respectively.