Use of norovirus genotype profiles to differentiate origins of foodborne outbreaks.
Because secondary transmission masks the connection between sources and outbreaks, estimating the proportion of foodborne norovirus infections is difficult. We studied whether norovirus genotype frequency distributions (genotype profiles) can enhance detection of the sources of foodborne outbreaks. Control measures differ substantially; therefore, differentiating this transmission mode from person-borne or food handler-borne outbreaks is of public health interest. Comparison of bivalve mollusks collected during monitoring (n = 295) and outbreak surveillance strains (n = 2,858) showed 2 distinguishable genotype profiles in 1) human feces and 2) source-contaminated food and bivalve mollusks; genotypes I.2 and I.4 were more frequently detected in foodborne outbreaks. Overall, approximately 21% of all outbreaks were foodborne; further analysis showed that 25% of the outbreaks reported as food handler-associated were probably caused by source contamination of the food.
Verhoef
Linda
L
National Institute for Public Health and the Environment (RIVM), Postbak 22, PO Box 1, 3720 BA Bilthoven, The Netherlands. linda.verhoef@rivm.nl
Vennema
Harry
H
van Pelt
Wilfrid
W
Lees
David
D
Boshuizen
Hendriek
H
Henshilwood
Kathleen
K
Koopmans
Marion
M
D000818:Animals; D049872:Bivalvia / Q000821:virology; D017250:Caliciviridae Infections / Q000453:epidemiology / Q000209:etiology / Q000821:virology*; D004196:Disease Outbreaks; D005243:Feces / Q000821:virology; D005502:Food / Q000821:virology; D005511:Food Handling / Q000592:standards; D005517:Foodborne Diseases / Q000453:epidemiology / Q000209:etiology / Q000821:virology*; D005759:Gastroenteritis / Q000453:epidemiology / Q000209:etiology / Q000821:virology*; D005814:Genes, Viral / Q000235:genetics; D005838:Genotype; D006801:Humans; D029322:Norovirus / Q000235:genetics*; D057096:Shellfish Poisoning / Q000821:virology