Heminested multiplex reverse transcription-PCR for detection and differentiation of Norwalk-like virus genogroups 1 and 2 in fecal samples

The present study describes a heminested multiplex reverse transcription (R T)-PCR assay which enables simultaneous detection and differentiation of No rwalk-like virus (NLV) genogroups from clinical fecal samples without the n eed to perform sequencing or hybridization. The assay developed was able to detect concentrations of fewer than 100 viral particles per 5 mul of clari fied fecal extract and could differentiate the two genogroups with a specif icity of 100%, Although the multiplex RT-PCR assay failed to detect NLV in about 3% of the fecal samples which were NLV positive by electron microscop y (EM), the assay was approximately; six times more sensitive than EM for N LV detection.