New Processing Method May Inactivate Human Norovirus Strains in Foods

06/02/07 High pressure processing may inactivate human norovirus strains in foods say researchers from the U.S. They report their findings in the January 2007 issue of the journal Applied and Environmental Microbiology.

Norovirus infection is a common problem worldwide with 40% of reported cases in the U.S. alone attributed to food borne outbreaks. Shellfish and produce are two sources most frequently associated with norovirus infections due to the fact that uncooked foods can often become contaminated following exposure to contaminated irrigation waters or after human handling in the case of produce. Currently, there is no adequate intervention for contaminated shellfish because viruses can remain live for several days. Lack of suitable laboratory animals and the ability to develop the virus in vitro has hampered many prior research attempts.

A recently identified strain of murine norovirus (MNV-1) was developed in vitro and has more biochemical, pathological, and molecular similarities to human noroviruses than any previously used for research. In the study MNV-1 was evaluated for susceptibility to high pressure processing ranging from 2 to 15 minutes at temperatures between 41 and 86 degrees Fahrenheit. Results showed that a 5 minute treatment differing in pressure range was sufficient to inactivate the virus at a variety of temperatures, however, researchers found that inactivation was enhanced when applied at refrigeration temperatures. This study also demonstrated that 5 minutes of high pressure processing at 41 degrees Fahrenheit completely inactivated the MNV-1 strain in oyster tissue.

"This work is the first demonstration that norovirus can be inactivated by high pressure and suggests good prospects for inactivation of nonpropagable human norovirus strains in foods," say the researchers.