title: Prevalence of human noroviruses in frozen marketed shellfish, red fruits and fresh vegetables.
abstract: Noroviruses (NoVs), currently recognised as the most common human food-borne pathogens, are ubiquitous in the environment and can be transmitted to humans through multiple foodstuffs. In this study, we evaluated the prevalence of human NoV genogroups I (GI) and II (GII) in 493 food samples including soft red fruits (n = 200), salad vegetables (n = 210) and bivalve mollusc shellfish (n = 83), using the Bovine Enterovirus type 1 as process extraction control for the first time. Viral extractions were performed by elution concentration and genome detection by TaqMan Real-Time RT-PCR (RT-qPCR). Experimental contamination using hepatitis A virus (HAV) was used to determine the limit of detection (LOD) of the extraction methods. Positive detections were obtained from 2 g of digestive tissues of oysters or mussels kept for 16 h in seawater containing 2.0-2.7 log10 plaque-forming units (PFU)/L of HAV. For lettuces and raspberries, the LOD was, respectively, estimated at 2.2 and 2.9 log10 PFU per 25 g. Of the molluscs tested, 8.4 and 14.4% were, respectively, positive for the presence of GI NoV and GII NoV RNA. Prevalence in GI NoVs varied from 11.9% for the salad vegetables samples to 15.5% for the red soft fruits. Only 0.5% of the salad and red soft fruits samples were positive for GII NoVs. These results highlight the high occurrence of human NoVs in foodstuffs that can be eaten raw or after a moderate technological processing or treatment. The determination of the risk of infection associated with an RT-qPCR positive sample remains an important challenge for the future.
authors.affiliation: ACTALIA, Groupe Sécurité des Aliments et Innovation Procédés, 23 Boulevard du 13 Juin 1944 BP2, 14310, Villers-Bocage, France.
authors.forename: Julie
authors.initials: J
authors.lastname: Loutreul
authors.forename: Catherine
authors.initials: C
authors.lastname: Cazeaux
authors.forename: Delphine
authors.initials: D
authors.lastname: Levert
authors.forename: Aline
authors.initials: A
authors.lastname: Nicolas
authors.forename: Sandrine
authors.initials: S
authors.lastname: Vautier
authors.forename: Anne Laure
authors.initials: AL
authors.lastname: Le Sauvage
authors.forename: Sylvie
authors.initials: S
authors.lastname: Perelle
authors.forename: Thierry
authors.initials: T
authors.lastname: Morin
mesh_terms: D000818:Animals; D002417:Cattle; D005506:Food Contamination / Q000706:statistics & numerical data*; D005638:Fruit / Q000821:virology*; D006801:Humans; D018545:Lactuca / Q000821:virology; D008974:Mollusca / Q000821:virology; D029322:Norovirus / Q000145:classification / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification*; D065856:Rubus / Q000821:virology; D012758:Shellfish / Q000191:economics / Q000821:virology*; D014675:Vegetables / Q000821:virology*