Prevalence of human noroviruses in frozen marketed shellfish, red fruits and fresh vegetables

Food Environ Virol. 2014 Sep;6(3):157-68. doi: 10.1007/s12560-014-9150-8. Epub 2014 Jun 13.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cattle
  • Food Contamination / statistics & numerical data*
  • Fruit / virology*
  • Humans
  • Lactuca / virology
  • Mollusca / virology
  • Norovirus / classification
  • Norovirus / genetics
  • Norovirus / growth & development
  • Norovirus / isolation & purification*
  • Rubus / virology
  • Shellfish / economics
  • Shellfish / virology*
  • Vegetables / virology*