Clinical Spectrum and Transmission Characteristics of Infection with Norwalk-Like Virus: Findings from a Large Community Outbreak in Sweden

A large foodborne outbreak caused by Norwalk-like virus (NLV) among children and staff at 30 day care centers provided an opportunity to study symptomatology and attack rates among patients in different age groups, as well as secondary transmission rates in centers and households. A retrospective co...

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Bibliographic Details
Published in:	Clinical infectious diseases 2001-09, Vol.33 (5), p.622-628
Main Authors:	Götz, Hannelore, Ekdahl, Karl, Lindbäck, Johan, de Jong, Birgitta, Hedlund, Kjell Olof, Giesecke, Johan
Format:	Article
Language:	eng
Subjects:	Adolescent Adult Adults Age Distribution Aged Biological and medical sciences Caliciviridae Infections - diagnosis Caliciviridae Infections - epidemiology Caliciviridae Infections - transmission Child Child, Preschool Children Community-Acquired Infections - diagnosis Community-Acquired Infections - epidemiology Community-Acquired Infections - transmission Diarrhea Disease Outbreaks Disease transmission Disease Transmission, Infectious Epidemiology Female Gastroenteritis Human viral diseases Humans Infant Infections Infectious diseases Major Articles Male Medical sciences Medicin och hälsovetenskap Middle Aged Norwalk virus - isolation & purification Retrospective Studies Risk Risk Factors Sweden - epidemiology Symptoms Viral diseases Viral diseases of the digestive system Vomiting
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Summary:	A large foodborne outbreak caused by Norwalk-like virus (NLV) among children and staff at 30 day care centers provided an opportunity to study symptomatology and attack rates among patients in different age groups, as well as secondary transmission rates in centers and households. A retrospective cohort study of 775 subjects from 13 randomly chosen centers was performed. Diarrhea was more common in adults than in children (P = .001), whereas the reverse was noted with regard to vomiting (P = .003). The primary attack rate was 27% (142 of 524 subjects): 54% of adults versus 19% of children (P < .001). The mean incubation time for foodborne cases of infection was 34 hours. The secondary attack rate was 17%. Risk factors for spread into households were the primary case being a child (relative risk [RR], 3.8; 95% confidence interval [CI], 1.9–7.6) and vomiting (RR, 2.4; 95% CI, 1.0–5.5). The incubation time for person-to-person transmission was approximated by a mean serial interval of 52 hours. This is the first reported outbreak of NLV infection in which secondary transmission into households by individuals has been studied.
ISSN:	1058-4838 1537-6591