$1 Million Study Tackles Role of Viruses in Safety of Fresh Produce

December 9, 2010

COLUMBUS, Ohio -- In a new four-year, $1 million study, Ohio State University scientists are leading an effort aimed at reducing the incidence of foodborne illness in fresh produce caused by viruses.

Viruses, including human norovirus, hepatitis A virus and rotavirus, account for more than two out of three foodborne illnesses worldwide. Yet most research and nearly all education about foodborne illness focuses on bacteria, such as Salmonella, E. coli, Listeria and Campylobacter.

According to the Centers for Disease Control and Prevention, noroviruses alone cause more than 21 million cases of acute gastroenteritis and account for more than half all foodborne disease outbreaks.

"Viruses, as they relate to food safety, are not well understood," said Jianrong Li, the project's principal investigator. "There's a real gap in the field that we will try to fill with this research."

Li is an assistant professor in Ohio State's Department of Food Science and Technology and scientist with the university's Ohio Agricultural Research and Development Center (OARDC). He has a joint appointment in the College of Public Health and was hired in 2008 as part of a special university-wide initiative, Public Health Preparedness in Infectious Disease (http://phpid.osu.edu).

The project, "An Integrated Approach to Prevent and Minimize Foodborne Enteric Viruses in Vegetables and Fruits," was one of two "Special Emphasis Grants" funded by the U.S. Department of Agriculture's National Integrated Food Safety Initiative. It is designed to take what is learned in the lab into the classroom and the field.

Fresh produce is at high risk of being contaminated by noroviruses. According to a CDC compilation of outbreak data in the U.S. from 1998 to 2006, norovirus has become the top cause of fresh produce-associated illnesses, accounting for more than 40 percent of outbreaks. Norovirus has contaminated lettuce, salad, fruit salad, tomatoes, carrots, melons, strawberries, raspberries, orange juice, fresh-cut fruit, spring onion and other types of produce. In addition, hepatitis A has contaminated onions, berries, carrots, salads and iceberg lettuce.

"Illnesses caused by noroviruses are widespread -- they are often known as 'cruise ship illness' because they spread easily in such settings," said Ken Lee, professor of food science and technology at Ohio State who is a co-principal investigator on the project. "They're rarely fatal, but can be so nasty that people affected might wish they were dead." Lee, who also has appointments with OARDC and OSU Extension, will coordinate the project's practical outcomes with members of the Center for Innovative Food Technology and Ohio State's Food Innovation Center.

The research portion of the project will examine how produce is contaminated in the first place, Li said. Scientists know that bacteria can contaminate plants through cuts or abrasions or through the plant's stomata, the pores that plants use for respiration. Viruses, which are about 1,000 times smaller than bacteria, may do the same, but also could contaminate produce through the root system. Contamination could take place during fertilization, irrigation, or handling by workers in the fields or during processing, or simply by being exposed to wildlife, soil or domestic animals.

The researchers will also test the effectiveness of different sanitizers and processing methods on removing or killing viruses from contaminated produce, whether the virus is on the surface or has entered the plant tissue. For this portion of the project, the team will grow green onions and Romaine lettuce in experimental conditions in a greenhouse, expose the seeds and plants to viruses, and after a period of time determine if the virus is still alive, and if it is, if it has remained on the surface of the plant or has entered the tissue. After produce is harvested, it is often cooled and stored in a vacuum container to preserve its freshness, but subjecting a piece of contaminated produce to vacuum pressure increases the likelihood that the virus will enter the plant tissue, Li said. This project will examine the effectiveness of three processing technologies -- gaseous ozone, E-beam irradiation, and high-pressure processing -- in inactivating viral pathogens.

Once the scientists have a deeper understanding of how viruses contaminate produce and what can be done to eradicate them, they will take their knowledge to growers and processors by Ohio State University Extension professionals. Doug Doohan, professor of horticulture and crop science and produce specialist for OSU Extension based at OARDC in Wooster, already leads an OSU Extension Fresh Fruit and Vegetable Food Safety Team, which has trained about 1,500 growers and packers in the past two years. In this project, Doohan will incorporate information about foodborne viruses into the Extension program, and will train growers and processors to minimize the viral contamination of fresh produce.

Finally, Li said, the researchers will develop a new course, "Foodborne Viruses and Food Safety," to be taught in Ohio State's Department of Food Science and Technology and College of Public Health, with the lesson plan, course modules, PowerPoint outline, website links and other course materials made available to other universities throughout the nation

"Currently, if you look at standard food microbiology textbooks, there is little mention of viruses," Li said. "If you look at virology texts, there is no mention of food safety. This project will help us train the next generation of food safety professionals."

The research team also includes experts at other universities: food virologists Lee-Ann Jaykus of North Carolina State University and Xi Jiang of the University of Cincinnati, and food engineers Haiqiang Chen of the University of Delaware and Roberto Uribe of Kent State University.

Caption for photo: Jianrong Li

 

Author(s): 
Martha Filipic
Source(s): 
Jianrong Li