Norwalk virus: How infectious is it

• Published in: Journal of medical virology Vol. 80; no. 8; pp. 1468 - 1476
• Main Authors: Teunis, Peter F.M, Moe, Christine L, Liu, Pengbo, Miller, Sara E, Lindesmith, Lisa, Baric, Ralph S, Le Pendu, Jacques, Calderon, Rebecca L
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.08.2008; Wiley-Liss
• Subjects: Biological and medical sciences; Caliciviridae Infections - genetics; Caliciviridae Infections - physiopathology; Caliciviridae Infections - transmission; Caliciviridae Infections - virology; dose response; Fundamental and applied biological sciences. Psychology; Gastroenteritis - genetics; Gastroenteritis - physiopathology; Gastroenteritis - virology; Human viral diseases; Humans; Infectious diseases; Medical sciences; Microbiology; Microscopy, Electron; Miscellaneous; Models, Biological; Monte Carlo Method; Norovirus; Norwalk virus; Norwalk virus - genetics; Norwalk virus - isolation & purification; Norwalk virus - pathogenicity; Norwalk virus - ultrastructure; primary inoculum; Reverse Transcriptase Polymerase Chain Reaction; Risk Assessment; RNA, Viral - analysis; secondary inoculum; Viral diseases; viral gastroenteritis; Virology; virus aggregation; Norovirus; Human calicivirus; Gastroenteritis; secondary inoculum; Virus; Aggregation; Infection; viral gastroenteritis; Calicivirus; virus aggregation; dose response; Caliciviridae; primary inoculum; Norwalk virus; Digestive diseases; Intestinal disease; Gastric disease
• ISSN: 0146-6615; 1096-9071; 1096-9071
• DOI: 10.1002/jmv.21237

Noroviruses are major agents of viral gastroenteritis worldwide. The infectivity of Norwalk virus, the prototype norovirus, has been studied in susceptible human volunteers. A new variant of the hit theory model of microbial infection was developed to estimate the variation in Norwalk virus infectivity, as well as the degree of virus aggregation, consistent with independent (electron microscopic) observations. Explicit modeling of viral aggregation allows us to express virus infectivity per single infectious unit (particle). Comparison of a primary and a secondary inoculum showed that passage through a human host does not change Norwalk virus infectivity. We estimate the average probability of infection for a single Norwalk virus particle to be close to 0.5, exceeding that reported for any other virus studied to date. Infected subjects had a dose-dependent probability of becoming ill, ranging from 0.1 (at a dose of 10³ NV genomes) to 0.7 (at 10⁸ virus genomes). A norovirus dose response model is important for understanding its transmission and essential for development of a quantitative risk model. Norwalk virus is a valuable model system to study virulence because genetic factors are known for both complete and partial protection; the latter can be quantitatively described as heterogeneity in dose response models. J. Med. Virol. 80:1468-1476, 2008.