CAFPA SPRING MEETING ON NOROVIRUSES
On March 30, 2010, the Capital Area Food Protection Association (CAFPA) held its spring meeting at the Grocery Manufacturers Association in Washington, DC. The meeting focused on noroviruses.
David Bergmire-Sweat (North Carolina Division of Public Health) spoke about epidemiological investigations of two norovirus outbreaks. He noted that humans are the only host for norovirus, which causes an estimated 23 million cases of gastroenteritis per year. An outbreak in Texas in 1998 associated with a university cafeteria. Of 125 ill students, 23 were hospitalized. This outbreak posed great challenges for investigators because of the variety of foods available in the cafeteria, but they were able to interview 36 ill students and 136 controls and found that deli sandwiches had a significant correlation with illness. Another norovirus outbreak Bergmire-Sweat discussed was in North Carolina in 2009 and associated with an oyster bar. The illness, totaling 280 cases, was linked to a single restaurant serving mainly oysters and traditional sides. The investigators screened samples of the restaurant staff’s stool for norovirus but found no positives. They ran a case study of 51 ill persons and 80 controls, which revealed that there was a significant correlation to steamed oysters. They reviewed the restaurant’s process of steaming oysters and found that the temperature range during steaming was not consistent and hot and cold spots were present within the oyster buckets. The next step in the investigation was to determine the source of these contaminated oysters. They determined the area was in Louisiana and that area was immediately shut down.
Dr. Marianne Miliotis (FDA Center for Food Safety and Applied Nutrition) related information on the risk profile of norovirus gathered from a review of the available science. Key information was shared, including norovirus’ stability over time at different temperatures, transmission, and eradication challenges. Norovirus remains intact longer in cold and moist conditions in which organic matter is present. It survives at a temperature of 140ºF for 30 minutes, is stable during freezing, and may survive in sterile water for up to one year. Norovirus is inactivated by boiling. Some sources of norovirus soil contamination include fertilizers, flooding, septic systems, and field workers. Control measures for norovirus include interruption of human transmission such as hand washing, not allowing ill workers to work, using hand barriers such as gloves, and isolation of the ill. She stressed that gel sanitizers for hands are not effective and that soap and water work well. The focus for industry should be reduction and prevention of transmission of norovirus by placing controls to address norovirus contamination throughout the product chain. Data gaps were also identified, and these include information on transmission in produce, attention to food workers and their role, and development of rapid, accurate methods to detect norovirus and determine viability.
Dr. Kalmia Kniel (University of Delaware) talked about research on viruses in pre-harvest environments. Surrogates including murine norovirus, hepatitis A, Aichi virus, and adenovirus 41 were used in the studies. The first study discussed was about survival in different land applied manures, which included poultry litter, pelletized poultry litter, dairy manure, bio-solids, and swine manure. The results showed that there was less degradation of virus at lower temperatures and in more aqueous manures. No survival was seen in the bio-solids. Kniel also noted that in general for the viruses, there was a decrease in infectivity over time. The current project underway is one on uptake of virus by leafy greens during production.
Dr. Gary Richards (USDA Agricultural Research Service) talked about his work on detection methods for norovirus. He has spent many years on this work and has had little success in propagating the virus using several different methods. He reviewed a simple, yet very time-consuming norovirus extraction that can be used with shellfish (a copy of the video is available from Richards at gary.richards@ars.usda.gov). He also reviewed processing controls for norovirus in shellfish. Relaying can be used, which is when shellfish are moved to a cleaner location to diffuse concentrated virus. Cooking and pasteurization work well in inactivating norovirus, but are an issue in consumer acceptability. Irradiation gives shellfish an off flavor. Freeze-thaw cycles can reduce norovirus by about 10% for each cycle. High pressure processing has been studied with human volunteers (to test the activity of surviving norovirus) and shows promising results when the pressure is increased to almost maximum pressure capacity (600 megapascals). A 3-log reduction could not be obtained using 400 megapascals.
Prepared by Emily Mathusa, Grocery Manufacturers Association