Norovirus (Norwalk Virus)

J Clin Microbiol. 2006 Nov;44(11):3878-82 Abstract quote

An international outbreak linked to oyster consumption involving a group of over 200 people in Italy and 127 total subjects in 13 smaller clusters in France was analyzed using epidemiological and clinical data and shellfish samples. Environmental information from the oyster-producing area, located in a lagoon in southern France, was collected to investigate the possible events leading to the contamination.

Virologic analyses were conducted by reverse transcription-PCR (RT-PCR) using the same primer sets for both clinical and environmental samples. After sequencing, the data were analyzed through the database operated by the scientific network FoodBorne Viruses in Europe. The existence of an international collaboration between laboratories was critical to rapidly connect the data and to fully interpret the results, since it was not obvious that one food could be the link because of the diversity of the several norovirus strains involved in the different cases.

It was also demonstrated that heavy rain was responsible for the accidental contamination of seafood, leading to a concentration of up to hundreds of genomic copies per oyster as detected by real-time RT-PCR.

Epidemiology
Disease Associations
Pathogenesis
Laboratory/Radiologic/ Other Diagnostic Testing
Gross Appearance and Clinical Variants
Histopathological Features and Variants
Special Stains/ Immunohistochemistry/ Electron Microscopy
Differential Diagnosis
Prognosis
Treatment
Commonly Used Terms
Internet Links

EPIDEMIOLOGY	CHARACTERIZATION
INCIDENCE
Widespread environmental contamination with Norwalk-like viruses (NLV) detected in a prolonged hotel outbreak of gastroenteritis. Cheesbrough JS, Green J, Gallimore CI, Wright PA, Brown DW. Preston Public Health Laboratory, Royal Preston Hospital, Lancashire, UK.	Epidemiol Infect 2000 Aug;125(1):93-8 Abstract quote A protracted outbreak of Norwalk-like virus (NLV)-associated gastroenteritis occurred in a large hotel in North-West England between January and May 1996. We investigated the pattern of environmental contamination with NLV in the hotel during and after the outbreak. In the ninth week, 144 environmental swabs taken from around the hotel were tested for NLV by nested RT-PCR. The sites were categorized according to the likelihood of direct contamination with vomit/faeces. The highest proportion of positive samples were detected in directly contaminated carpets, but amplicons were detected in sites above 1.5 m which are unlikely to have been contaminated directly. The trend in positivity of different sites paralleled the diminishing likelihood of direct contamination. A second environmental investigation of the same sites 5 months after the outbreak had finished were all negative by RT-PCR. This study demonstrates for the first time the extent of environmental contamination that may occur during a large NLV outbreak.
GEOGRAPHY
Distinct epidemiological patterns of Norwalk-like virus infection. Hale A, Mattick K, Lewis D, Estes M, Jiang X, Green J, Eglin R, Brown D. Enteric and Respiratory Virus Laboratory, Central Public Health Laboratory, London, United Kingdom.	J Med Virol 2000 Sep;62(1):99-103 Abstract quote Norwalk-like viruses (NLV) are important economically as a cause of both sporadic gastroenteritis in the community and large outbreaks in hospitals and other institutional settings. Despite the description of several antigenic types relatively little is known about the epidemiology of these individual types. NLVs were detected by electron microscopy in faecal specimens from 706 outbreaks of gastroenteritis that represented 68% of all outbreaks of non-bacterial gastroenteritis. These outbreaks took place in the counties of West and North Yorkshire and Humberside during six winter seasons between July 1992 and June 1998. NLV strains from 671 outbreaks were typed by antigen capture enzyme linked immunosorbent assays (ELISA) based on antisera made to recombinant virus-like particles of three antigenically distinct NLVs; Norwalk (NV), Mexico (MXV) and Grimsby (GRV) viruses. GRV was the predominant strain for five of the six winter seasons and overall was associated with 61% of NLV outbreaks. MXV was responsible for a single epidemic peak in the winter of 1993/94 but was also observed at other times throughout the study period. NV was only associated with two outbreaks in 1994 that were epidemiologically linked. Strains from the remaining 32% of outbreaks were non-reactive in all three ELISA. Thus, a single NLV antigenic type seems to have predominated during the period 1992 to 1998 in the UK.
Clinical spectrum and transmission characteristics of infection with Norwalk-like virus: findings from a large community outbreak in Sweden. Gotz H, Ekdahl K, Lindback J, de Jong B, Hedlund KO, Giesecke J. Department of Epidemiology, Swedish Institute for Infectious Diseases Control, Stockholm, Sweden.	Clin Infect Dis 2001 Sep 1;33(5):622-8 Abstract quote A large foodborne outbreak caused by Norwalk-like virus (NLV) among children and staff at 30 day care centers provided an opportunity to study symptomatology and attack rates among patients in different age groups, as well as secondary transmission rates in centers and households. A retrospective cohort study of 775 subjects from 13 randomly chosen centers was performed. Diarrhea was more common in adults than in children (P=.001), whereas the reverse was noted with regard to vomiting (P=.003). The primary attack rate was 27% (142 of 524 subjects): 54% of adults versus 19% of children (P<.001). The mean incubation time for foodborne cases of infection was 34 hours. The secondary attack rate was 17%. Risk factors for spread into households were the primary case being a child (relative risk [RR], 3.8; 95% confidence interval [CI], 1.9-7.6) and vomiting (RR, 2.4; 95% CI, 1.0-5.5). The incubation time for person-to-person transmission was approximated by a mean serial interval of 52 hours. This is the first reported outbreak of NLV infection in which secondary transmission into households by individuals has been studied.

DISEASE ASSOCIATIONS	CHARACTERIZATION
OYSTERS
Detection of multiple noroviruses associated with an international gastroenteritis outbreak linked to oyster consumption. Le Guyader FS, Bon F, DeMedici D, Parnaudeau S, Bertone A, Crudeli S, Doyle A, Zidane M, Suffredini E, Kohli E, Maddalo F, Monini M, Gallay A, Pommepuy M, Pothier P, Ruggeri FM. Laboratoire de Microbiologie, Institut Francais pour la Recherche et l'Exploitation de la Mer, Nantes, France.	J Clin Microbiol. 2006 Nov;44(11):3878-82 Abstract quote An international outbreak linked to oyster consumption involving a group of over 200 people in Italy and 127 total subjects in 13 smaller clusters in France was analyzed using epidemiological and clinical data and shellfish samples. Environmental information from the oyster-producing area, located in a lagoon in southern France, was collected to investigate the possible events leading to the contamination. Virologic analyses were conducted by reverse transcription-PCR (RT-PCR) using the same primer sets for both clinical and environmental samples. After sequencing, the data were analyzed through the database operated by the scientific network FoodBorne Viruses in Europe. The existence of an international collaboration between laboratories was critical to rapidly connect the data and to fully interpret the results, since it was not obvious that one food could be the link because of the diversity of the several norovirus strains involved in the different cases. It was also demonstrated that heavy rain was responsible for the accidental contamination of seafood, leading to a concentration of up to hundreds of genomic copies per oyster as detected by real-time RT-PCR.
An outbreak of Norwalk virus gastroenteritis associated with eating raw oysters. Implications for maintaining safe oyster beds. Kohn MA, Farley TA, Ando T, Curtis M, Wilson SA, Jin Q, Monroe SS, Baron RC, McFarland LM, Glass RI. Epidemic Intelligence Service, Centers for Disease Control and Prevention, Atlanta, GA.	JAMA 1995 Feb 8;273(6):466-71 Abstract quote OBJECTIVE--To determine the characteristics and the cause of an outbreak of gastroenteritis associated with eating raw oysters. DESIGN--Survey of groups of persons reporting illness to the health department after eating oysters; survey of convenience sample of oyster harvesters; and tracing of implicated oysters. SETTING--General community. MAIN OUTCOME MEASURES--Relative risk for illness after oyster consumption, source bed of contaminated oysters, presence of antibodies to Norwalk virus in serum, presence of a Norwalk virus in stool by direct electron microscopy and reverse transcription-polymerase chain reaction (RT-PCR), and DNA sequences of RT-PCR products. RESULTS--Seventy (83%) of 84 persons who ate raw oysters became ill vs three (7%) of 43 people who did not eat raw oysters (relative risk, 11.9; 95% confidence interval, 4.0 to 34.2). Eleven (79%) of 14 serum pairs had at least a fourfold increase in antibody to Norwalk virus. All 12 stool samples tested were positive by electron microscopy and/or RT-PCR for Norwalk virus. The RT-PCR products from all seven stool samples tested had identical DNA sequences. Implicated oysters were harvested November 9 through 13, 1993, from a remote oyster bed. Crews from 22 (85%) of 26 oyster harvesting boats working in this area reported routine overboard disposal of sewage. One harvester with a high level of antibodies to Norwalk virus reported having gastroenteritis November 7 through 10 and overboard disposal of feces into the oyster bed. CONCLUSIONS--This outbreak was caused by contamination of oysters in the oyster bed, probably by stool from one or more ill harvesters. Education of oyster harvesters and enforcement of regulations governing waste disposal by oyster harvesting boats might prevent similar outbreaks.
MINERAL WATER
Norwalk-like virus sequences in mineral waters: one-year monitoring of three brands. Beuret C, Kohler D, Baumgartner A, Luthi TM. Cantonal Food Laboratory of Solothurn, CH-4500 Solothurn, Switzerland.	Appl Environ Microbiol 2002 Apr;68(4):1925-31 Abstract quote In a recent study, RNA with nucleotide sequeces specific for "Norwalk-like viruses" (NLV) was detected in 11 different brands of European mineral waters. To clarify this finding, a 1-year monitoring study was conducted. Samples of three European brands of mineral water without gas were monitored weekly by reverse transcriptase PCR using generic and genogroup-specific oligonucleotides. Additional analyses were performed to investigate a possible correlation between NLV sequence contamination and mineral water lot numbers, the long-term stability (persistence) of NLV sequences in mineral water, and the level of contamination. NLV sequences were detected in 53 of 159 samples analyzed (33%) and belonged entirely to genogroup II. Although all NLV strains identified were closely related, three mineral water brand-specific clusters could be identified for both primer systems by sequencing. Analyses of second samples from lots previously shown to be positive for NLV sequences gave corresponding results in 45 of 53 cases (85%) (within a six-pack). NLV persistence was tested by analyzing 10 positive samples after 6 and 12 months of storage in darkness at room temperature. After 6 months, all samples remained positive; after 12 months, 9 of 10 samples were still positive for NLV sequences. No NLV sequences could be detected by analysis of 0.1-liter aliquots of 53 samples shown to be positive by testing of 1-liter volumes. Based on this fact and a test sensitivity of approximately 10 viral units, levels of contamination in positive mineral water samples were estimated to be in the range of 10 to 100 genomic equivalents per liter.

LABORATORY/ RADIOLOGIC/ OTHER TESTS	CHARACTERIZATION
RADIOLOGIC
LABORATORY MARKERS
RT-PCR ELISA
Detection and differentiation of Norwalk virus by reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay. Tatsumi M, Nakata S, Sakai Y, Honma S, Numata-Kinoshita K, Chiba S. Department of Pediatrics, Sapporo Medical University School of Medicine, Sapporo, Japan.	J Med Virol 2002 Oct;68(2):285-90 Abstract quote We have developed a reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay (RT-PCR-ELISA), using genetic cluster-specific probes in a microtiter plate format, for the detection and differentiation of Norwalk virus (NV) in stool samples. The specificity of the RT-PCR-ELISA was confirmed by testing 76 stool specimens and 15 tissue culture fluids derived from growths of unrelated viruses. The sensitivity of the RT-PCR-ELISA was compared with conventional PCR and Southern hybridization by testing the four cDNA clones derived from the RNA-dependent RNA polymerase region of the NV68 (NV/GI) virus and viruses in the NV/GII/P1B, the NV/GII/P2A, and the NV/GII/P2B cluster. This assay was as sensitive as the conventional RT-PCR with Southern hybridization regardless of primer pairs and probes used in the experiments. However, the actual sensitivity of this method was higher when clinical stool samples were examined because this assay examines all the samples irrespective of the RT-PCR results. The RT-PCR-ELISA format is simple, time saving, and suitable for testing many samples. It should be reliable for large-scale epidemiological studies of NV.
Genogroup-specific PCR primers for detection of Norwalk-like viruses. Kojima S, Kageyama T, Fukushi S, Hoshino FB, Shinohara M, Uchida K, Natori K, Takeda N, Katayama K. Section of Infectious Disease, R&D Center, BML, 1361-1, Matoba, Kawagoe, Saitama 350-1101, Japan.	J Virol Methods 2002 Feb;100(1-2):107-14 Abstract quote Norwalk-like viruses (NLV) are a major causative agent of nonbacterial gastroenteritis. There are still many NLV strains that are refractory to gene amplification by ordinary reverse transcription-polymerase chain reaction. This is due mainly to the genetic diversity among NLV, especially mismatches in the primer sequences, which limits this technique in clinical utility. In this study, improved primer sets based on the capsid region, to detect both genogroup I and II NLV by genogroup-specific manner, were developed. When stool specimens from gastroenteritis patients, that were positive for NLV by electron microscopy, were tested by this new primer set, all specimens were positive by RT-PCR. Primers described previously for RdRp and capsid protein were capable of amplifying the specimens by 31 and 77%, respectively. Therefore, new primer sets are extremely useful for the amplification and rapid diagnosis of nonbacterial gastroenteritis due to NLV as well as for epidemiological studies.

PROGNOSIS AND TREATMENT	CHARACTERIZATION
PROGNOSTIC FACTORS
TREATMENT
VACCINE
Norwalk virus vaccines: challenges and progress. Estes MK, Ball JM, Guerrero RA, Opekun AR, Gilger MA, Pacheco SS, Graham DY. 1Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA.	J Infect Dis 2000 May;181 Suppl 2:S367-73 Abstract quote Human caliciviruses (HuCVs) are the major cause of outbreaks of acute nonbacterial gastroenteritis throughout the world. An increasing recognition of the clinical significance of these viruses as human pathogens causing foodborne and waterborne disease indicates that an effective vaccine would be useful. This article reviews the current challenges that exist for the development of a vaccine for the HuCVs as well as the status of development of a candidate vaccine. HuCVs are viruses that exhibit a restricted tropism for infection of the gastrointestinal tract of humans, and a volunteer model of infection and disease is available. As pathogens with a restricted host range, the HuCVs are excellent models for understanding the mechanisms that mediate and regulate viral infection of the gastrointestinal tract and mucosal immunity in humans.