Rapid Detection of Norovirus from Fecal Specimens by Real-Time Reverse Transcription-Loop-Mediated Isothermal Amplification Assay

ABSTRACT In this study, we developed a one-step, single-tube genogroup-specific reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay for the detection of norovirus (NoV) genomes targeting from the C terminus of the RNA-dependent RNA polymerase gene to the capsid N-terminal/shell domain region. This is the first report on the development of an RT-LAMP assay for the detection of NoV genomes. Because of the diversity of NoV genotypes, we used 9 and 13 specially designed primers containing mixed bases for genogroup I (GI) and II (GII), respectively. The RT-LAMP assay had the advantages of rapidity, simplicity, specificity, and selectively and could obtain results within 90 min, generally even within 60 min, under isothermal conditions at 62°C. The detection limits for NoV genomes were between 102 and 103 copies/tube for GI and GII with differentiation by genotype, and no cross-reactions among NoV GI and GII and other gastroenteritis viruses, such as sapovirus, human astrovirus, adenovirus type 40 and 41, and group A and C rotavirus, were found. In the evaluation tests with fecal specimens obtained from gastroenteritis outbreaks, the sensitivity and specificity of the RT-LAMP assay with regard to RT-PCR were 100 and 94% for GI and 100 and 100% for GII, respectively. These findings establish that the RT-LAMP assay is potentially useful for the rapid detection of NoV genomes from fecal specimens in outbreaks of food-borne and person-to-person-transmitted gastroenteritis.