Study highlights method to enhance detection of norovirus

Clinical laboratories can improve detection of norovirus by testing with a newly developed molecular test method, according to a recently published study conducted by the State Hygienic Laboratory at The University of Iowa.

This month's issue of Journal of Virological Methods features the study, "Optimization of a real-time RT-PCR assay reveals an increase of genogroup 1 norovirus in the clinical setting." It was written by Anna Van Stelten, Emerging Infectious Disease fellow; Lucy DesJardin, Ph.D., program manager of Molecular Research and Development; Nancy Hall, supervisor of Environmental Microbiology; and Trisha Kreman, health lab specialist. This study was also presented at a poster session at the annual Association of Public Health Laboratories meeting in June of this year, where it was awarded first prize.

Noroviruses are the most common cause of food-borne outbreaks and gastroenteritis in the United States, causing approximately 23 million reported illnesses each year. The study demonstrates how using the SHL developed test using real-time RT-PCR methodology can increase the detection rate of these viruses in patient specimens.

"While a large percentage of gastroenteritis outbreaks have been associated with norovious infection, many suspect cases are not laboratory confirmed in clinical specimens submitted for testing," the report noted. "For example, it was estimated [that] 267 million episodes of diarrhea occur among adults in the United States annually, and an etiologic agent is only identified in less than 10 percent of these cases."

As part of the study, the Hygienic Lab scientists assembled 13 human clinical norovirus sequences representing eight genotypes of genogroup 1. This data was used to manually design primers and probes.

"The most critical factor of this study was the development of a new primer/probe set based upon current sequence data from a collection of clinical isolates," the study reported. "The data reflects [that] the optimized oligonucleotides [single-stranded DNA molecules] contribute to a substantial enhancement in assay performance characteristics.”