Microbiology Unit, Department of Clinical Pathology, Ain Shams University Hospitals, Cairo, Egypt
Received Date: June 24, 2012; Accepted Date: June 25, 2012; Published Date: June 27, 2012
Citation: Zaghloul MZ (2012) Noroviruses as a Cause of Nonbacterial Gastroenteritis . Air Water Borne Dis 1:e117. doi:10.4172/2167-7719.1000e117
Copyright: © 2012 Zaghloul MZ . This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Noroviruses (NoV) are major causes of acute nonbacterial gastroenteritis and a major public health concern [1]. Noroviruses (NoV) are members of the family Caliciviridae, they are single-stranded RNA, non enveloped viruses [2] with three major open reading frames (ORFs) that encode non structural capsid and minor structural proteins, respectively [3]. Since the first identification of this pathogen in 1972 [4], NoV have become one of the most commonly reported causative agents of large outbreaks of nonbacterial gastroenteritis worldwide [5]. NoV infection relies on the interaction of the viruses with histo-blood group antigens (HBGAs) as host receptors [6]. Based on antigenic and genetic distinctions NoV (formerly called Norwalk- like viruses) can be divided into 5 different genogroups including 29 genetic clusters (subtypes): 8 in genogroup I (GI), 17 in GII, 2 in GIII and 1 each in GIV and GV [7]. Moreover, worldwide, the GII-4 genotype (Bristol virus like genotype) has been shown to be the predominant strain of NoV associated with gastroenteritis [8,9].
Human associated NoV outbreaks resulting from ingestion of contaminated food, such as raw oysters [10] and water [11] or by person to person transmission in semi closed communities such as hospitals, schools, nursing homes and cruise ships [12]. NoV usually cause acute self-limited infections in human of all ages. However NoV infection can be severe in elderly persons, young children and immuno compromised persons. After an incubation period of 1 to 3 days, the clinical manifestations are characterized by diarrhea that lasts 12 to 60 hours accompanied by other symptoms such as nausea, vomiting, abdominal cramps, headache and low-grade fever [13].
Direct and immune electron microscopy (EM) were used to detect the presence of NoV in faecal specimens, but EM is not routinely implemented in the laboratory because of technical limitations , dependency on trained medical staff for its operation [2] and low sensitivity as it requires at least 106 viral particles per ml of stool [14]. Norovirus can infect and replicate in a physiologically relevant 3- dimensional, organoid model of human small intestine epithelium [15]. Enzyme linked immunosorbent assay could be used for the screening of stool samples for NoV because of its simplicity [16]. Recently realtime reverse transcription-PCR was used for detection of GI and GII NoV from stool samples using Taq Man probes [17,18] or SYBR Green [19]. A sensitive colorimetric reverse transcription loop-mediated isothermal amplification (RT-LAMP) method was established to detect norovirus genotype GII. The method employed a set of six specially designed primers that recognized eight distinct sequences of RNAdependant RNA polymerase and capsid protein gene [20].
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