A Center for Produce Safety grant will fund University of Georgia (UGA) research aimed at studying human norovirus and its impact on leafy vegetables, in particular, lettuce.
Malak Esseili, an Assistant Professor at the Center for Food Safety on the UGA Griffin campus, is the lead investigator in the project, which spans from Jan. 1, 2021 through Jan. 1, 2023. Her objective is to study the survival rate of human norovirus in river water, which is commonly used in agricultural irrigation; analyze its die-off rate in relation to E. coli (a standard water quality fecal indicator organism); determine the survival of infectious virus on lettuce under pre-harvest; and on post-harvest lettuce following chlorine washes.
Human Norovirus Top Food-Borne Pathogen
“Norovirus in the U.S. is the No. 1 food-borne pathogen; 58% of foodborne illnesses are caused by human norovirus. It’s very prevalent, but there is unfortunately no vaccine or antiviral drugs to treat norovirus infections. Most of the foodborne outbreaks, historically, are associated with leafy greens, particularly lettuce or frozen berries, such as strawberries. If it’s frozen, the virus will likely be preserved,” Esseili said. “It’s really important to understand whether norovirus on leafy greens, such as lettuce, remains infectious or not and to what level.”
Understanding Norovirus
She said that the human norovirus is excreted with feces. If infected, sick people can shed the virus in their feces, and all the feces travels down the sewer to a treatment plant. But the treatment plant is not 100% effective in removing this virus. This leads to contaminated river water, which can be used in watering crops like lettuce.
“The water that comes out after the treatment of human waste, that water is called effluent, and it goes into a river. Many studies around the world have detected genetic material of the virus in river water. However, because we did not have a cell culture method for norovirus, we could not determine whether finding virus-specific genetic materials indicate the presence of infectious virus or not. We don’t know how long the virus remains infectious in river water and this is what my grant will also be looking at,” Esseili said.
Esseili’s Experiment
Esseili said that her experimental work will consist of growing lettuce in greenhouses and adding drops of the virus on the lettuce leaves in small quantities. Then, she will monitor the infectivity of the virus using a recently discovered cell culture method for human norovirus. Some of the basic questions she wants to answer are, does the pathogen survive and for how long? And will regular water clean it off or does it require a sanitation step such as chlorine washings.
This research will help prevent illnesses associated with norovirus. It’s such a dangerous pathogen that even a low dose can be problematic.
“If you have even low quantities of the virus on the leafy greens or berries and the person eats it, there is a chance the person will get infected,” Esseili said.