A food poisoning outbreak caused by purple Washington clam contaminated with norovirus (Norwalk-like virus) and hepatitis A virus

A party of 57 people dined together in a restaurant in Hamamatsu City on December 11, 2001. The next day, 22 of them developed symptoms of acute gastroenteritis, such as diarrhea, vomiting, and fever. Examination of 4 fecal specimens from these patients by ELISA for Norovirus (Norwalk-like virus, NV) detected both genogroup I (GI) and genogroup II (GII) NV in all the 4 specimens. In addition, RT-PCR and real-time PCR methods for NV detected the NV gene. Approximately one month after the outbreak of the food poisoning (acute gastroenteritis) by NV, 4 individuals in the same party developed type A hepatitis. Both RT-PCR and real-time PCR methods for hepatitis A virus (HAV) detected the HAV gene in their fecal specimens. The party of these patients ate purple Washington clam (Saxidomus purpuratus, imported from China) steamed with red pepper. Since this food appeared to have caused the viral infections, the one with the same lot number was subjected to viral examinations, which successfully detected the NV GI, NV GII, and HAV genes. These results led to the conclusion that the clam contaminated with NV and HAV had caused the food poisoning. The DNA sequences of the NV detected in the patients and the clam had 74 to 99% homology, indicating strains of various genotypes. All the strains of HAV that were derived from the patients and the clam were genotype 1A, and these sequences had over 95% homology, but were not completely identical. This outbreak led to the demonstration of imported fishery products as a cause of type A hepatitis, and indicated the need for guiding and enlightening people on the importance of adequate cooking of bivalves.     

Rotavirus outbreak on a pediatric oncology floor: possible association with toys

BACKGROUND: Several outbreaks of rotavirus gastroenteritis have occurred in hospitals and day care centers. In the spring of 1997, an outbreak of rotavirus occurred on our pediatric unit. Aggressive infection control measures were instituted, and potential lapses in infection control were assessed. METHODS: Memorial Sloan-Kettering Cancer Center is a 434-bed cancer hospital in New York City. The pediatric unit is a 42-bed ward with both bone marrow transplant patients and non-bone marrow transplant oncology patients. Nosocomially acquired rotavirus was defined as diarrhea, vomiting, or gastrointestinal upset with onset 48 hours or more after hospital admission, accompanied by a positive enzyme immunoassay for rotavirus antigen. RESULTS: Between February 24 and April 4, 1997, 8 patients on the pediatric unit had nosocomial rotavirus. Aggressive infection control measures were instituted. Patients with rotavirus were cohorted and placed on contact precautions (strict handwashing, gloves, and gown). Investigation by the infection control team revealed that communal toys in the playroom were not being cleaned according to the weekly protocol. CONCLUSIONS: An outbreak of nosocomial rotavirus occurred on our pediatric oncology unit. Shared toys may have served as fomites in the transmission of rotavirus.     

Effects of handwashing on Feline Calicivirus removal as Norovirus surrogate

Viral gastroenteritis caused by Norovirus (NV) mainly appears during the winter season. In fact, outbreaks and patients with NV gastroenteritis are the major cause of community disease in the winter. Strategies to avoid gastroenteritis caused by NV are thus needed. No effective method for evaluating virus inactivation and removal exists for of NV, which cannot be cultured using cell-lines. Trials using Feline Calici Virus (FCV; a member of the calicivirus family) as a NV surrogate have been conducted by culturing FCV in CRFK cells. By washing one's hands, about 99% of the viruses can be removed, compared with simply rinsing one's hands in running water. Washing one's hands with alcohol, chlorhexidine, quaternary ammonium, or 3 other kinds of hand soaps (containing povidone-iodine, triclosan, and isopropylmethyl phenol, respectively), was also effective for removing viruses. These results suggest that washing one's hands may be an effective method of preventing viral gastroenteritis.     

Comparison of the number of Norovirus genome copies in patients and healthy persons

In viral gastroenteritis outbreaks occurred by Norovirus (NV), NV was detected not only from patients but also from healthy persons who have taken the same food, and also detected from healthy staff members working at community places such as hospital, school and nursing home. The number of fecal NV genome copies of patients, healthy persons and food handlers are examined by real-time PCR method, to investigate foodborne gastroenteritis and person to person transmission outbreaks. There is no significant difference on the number of NV genome copies in feces between patients, and NV-detected healthy persons. Those result indicate asymptomatic carrier of NV who were working as food handlers or staff members at community places will become an origin of food-borne gastroenteritis or person to person transmission outbreaks.     

Association of histo-blood group antigens and susceptibility to norovirus infections

BACKGROUND: Noroviruses (NoVs) are the leading cause of viral gastroenteritis in humans of all ages. Challenge studies that used the NoV prototype strain Norwalk virus (NV) have shown that some individuals are not susceptible to infection, suggesting the absence of a receptor. Recent studies have identified histo-blood group antigens (HBGAs) as possible receptors. Being a nonsecretor and presence of HBGA type B were associated with protection against infection with NV, a genogroup (GG) I NoV. METHODS: In the present retrospective study, we investigated the association between presence of HBGAs and the risk of infection with another NoV belonging to GGI (Hu/NV/I/Birmingham/93/UK). The study was done as part of an investigation of a waterborne outbreak in a group of schoolchildren and of a cohort of healthy adults. The ABH histo-blood group phenotype was determined by use of saliva or serum samples from these individuals. RESULTS: Presence of HBGA type B was significantly correlated with a lack of susceptibility to infection with GGI NoV and with an absence of antibodies. No correlation was found with GGII NoV. Although the infection rate in nonsecretors was lower, this difference was not statistically significant, and several children lacking HBGAs in saliva were found to be infected. CONCLUSIONS: Individuals with the HBGA type B may be protected against infection with GGI (but not GGII) NoVs. The association between susceptibility to NoV infection and being a secretor may be restricted to GGI NoV.     

Replication and packaging of Norwalk virus RNA in cultured mammalian cells

Human noroviruses, the most common cause of nonbacterial gastroenteritis, are characterized by high infectivity rate, low infectious dose, and unusually high stability outside the host. However, human norovirus research is hindered by the lack of a cell culture system and a small animal model of infection. Norwalk virus (NV) is the prototype strain of human noroviruses. We report here replication of NV viral RNA and its packaging into virus particles in mammalian cells by intracellular expression of native forms of NV viral RNA devoid of extraneous nucleotide sequences derived from the expression vector by the use of replication-deficient vaccinia virus MVA encoding the bacteriophage T7 RNA polymerase (MVA/T7). Expressed genomic RNA was found to replicate; NV subgenomic RNA was transcribed from genomic RNA by use of NV nonstructural proteins expressed from genomic RNA and was subsequently translated into NV capsid protein VP1. Viral genomic RNA was packaged into virus particles generated in mammalian cells. The cesium chloride (CsCl) density gradient profile of virus particles containing genomic RNA was similar to that of NV purified from stool. These observations indicate that the NV cDNA constructed here is a biologically infectious clone, and that mammalian cells have the ability to replicate NV genomic RNA. This work establishes a mammalian cell-based system for analysis of human norovirus replication and, thus, makes it feasible to investigate antiviral agents in mammalian cells.     

A large nontypical outbreak of Norwalk virus. Gastroenteritis associated with exposing celery to nonpotable water and with Citrobacter freundii.

The US Air Force Academy experienced a point-source outbreak of gastroenteritis originally believed to be caused by Salmonella. The overall attack rate was 48% among approximately 3000 cadets and staff. Food-specific attack rates implicated chicken salad. The odds ratio for chicken salad consumption in ill cadets was 10.7 (95% confidence interval: 8.2; 13.8). The celery component had been exposed to nonpotable water. Citrobacter freundii were statistically associated with consumption of the suspected vehicle and subsequent illness. Most aspects were consistent with the epidemiology of Norwalk gastroenteritis. However, the clinical presentation was not typical of reported outbreaks. One hundred five cadets required intravenous rehydration. Serum samples implicated Norwalk virus as the most probable cause of this outbreak. The Centers for Disease Control (Atlanta, Ga) recently began national surveillance for viral gastroenteritis. All outbreaks of gastroenteritis associated with nonpotable water should be investigated for evidence of viral cause.     

Chimpanzees as an animal model for human norovirus infection and vaccine development

Noroviruses are global agents of acute gastroenteritis, but the development of control strategies has been hampered by the absence of a robust animal model. Studies in chimpanzees have played a key role in the characterization of several fastidious hepatitis viruses, and we investigated the feasibility of such studies for the noroviruses. Seronegative chimpanzees inoculated i.v. with the human norovirus strain Norwalk virus (NV) did not show clinical signs of gastroenteritis, but the onset and duration of virus shedding in stool and serum antibody responses were similar to that observed in humans. NV RNA was detected in intestinal and liver biopsies concurrent with the detection of viral shedding in stool, and NV antigen expression was observed in cells of the small intestinal lamina propria. Two infected chimpanzees rechallenged 4, 10, or 24 mo later with NV were resistant to reinfection, and the presence of NV-specific serum antibodies correlated with protection. We evaluated the immunogenicity and efficacy of virus-like particles (VLPs) derived from NV (genogroup I, GI) and MD145 (genogroup II, GII) noroviruses as vaccines. Chimpanzees vaccinated intramuscularly with GI VLPs were protected from NV infection when challenged 2 and 18 mo after vaccination, whereas chimpanzees that received GII VLPs vaccine or a placebo were not. This study establishes the chimpanzee as a viable animal model for the study of norovirus replication and immunity, and shows that NV VLP vaccines could induce protective homologous immunity even after extended periods of time.     

Norovirus gastroenteritis general outbreak associated with raw shellfish consumption in South Italy

Background  

Despite Noroviruses (NV, previously "Norwalk-like viruses") being a leading cause of acute gastroenteritis outbreaks, the impact of NV infection is at present unknown and little information is available about strains circulating in Italy. In April 2002 an outbreak of gastroenteritis occurred in the province of Bari (South-east Italy), involving several households.     

Incidence and prevalent types of Norwalk virus, Sapporo virus and human astrovirus in pediatric gastroenteritis in Hiroshima Prefecture

The incidence and prevalent types of Norwalk virus (NV), Sapporo virus (SV), and human astrovirus (HAstV) in pediatric gastroenteritis in Hiroshima Prefecture were investigated in 7 cold seasons, between 1995/96 and 2001/02. The incidences of NV, SV, and HAstV were 23.6% ranging from 16.3 to 34.4, 2.5% ranging from 1.5 to 4.7, and 3.2% ranging from 1.5 to 6.0, respectively. The peak of the incidence of NV was found in November and December. No accumulation of monthly incidence in SV or HAstV was noted. Most NVs detected belonged to genogroup II. A probe type of G2F, according to Fukuda et al., was predominant in NV, followed by G2E and G2B. The probe types of LON and SAP, according to Vinje et al., were predominant in SV. Serotype 1 was predominant in HAstV.     

Norovirus gastroenteritis causes severe and lethal complications after chemotherapy and hematopoietic stem cell transplantation

Norovirus (NV) infections are a frequent cause of gastroenteritis (GE), but data on this disease in immunocompromised patients are limited. We analyzed an NV outbreak, which affected immunosuppressed patients in the context of chemotherapy or HSCT. On recognition, 7 days after admission of the index patient, preventive measures were implemented. Attack rates were only 3% (11/334) and 10% (11/105) among patients and staff members, respectively. The median duration of symptoms was 7 days in patients compared with only 3 days in staff members (P = .02). Three patients died of the NV infection. Commonly used clinical diagnostic criteria (Kaplan-criteria) were unsuitable because they applied to 11 patients with proven NV-GE but also to 15 patients without NV-GE. With respect to the therapeutic management, it is important to differentiate intestinal GVHD from NV-GE. Therefore, we analyzed the histopathologic patterns in duodenal biopsies, which were distinctive in both conditions. Stool specimens in patients remained positive for NV-RNA for a median of 30 days, but no transmission was observed beyond an asymptomatic interval of 48 hours. NV-GE is a major threat to patients with chemotherapy or HSCT, and meticulous measures are warranted to prevent transmission of NV to these patients.     

Rotavirus infection in a geriatric population

An outbreak of gastroenteritis affected 19 of 34 geriatric patients and four of 23 staff assigned to the ward in a period of 3 1/2 weeks in January 1980. Fourteen of the 19 patients with gastroenteritis (17 were tested properly) and four of the ten asymptomatic patients (five asymptomatic patients were not tested) showed evidence of rotavirus infection by virus positivity and/or a significant antibody response to rotavirus. One of the four staff members with gastroenteritis showed serologic evidence (three were tested) of rotavirus infection. Nine of the 18 asymptomatic staff members (two remaining staff members were not tested) showed a fourfold rise in antibody to rotavirus but four had antibody titers of 1:32 or more. The patients had diarrhea for a mean of 2.6 days. Most of them had five or fewer diarrheal stools in one day. Six patients had a severe illness and two died. Thirteen of 15 symptomatic patients who had serum samples, collected during the acute and convalescent phases, tested manifested high titers (greater than or equal to 1:32) of complement-fixing antibody to rotavirus antigen.     

Dengue outbreak in Swat and Mansehra,Pakistan 2013;an epidemiological and diagnostic perspective

Objective:To High light some epidemiological,clinical and diagnostic features of dengue fever during an outbreak and the role of different diagnostic techniques to achieve the highest level of accuracy in results.Methods:Blood samples(n=323) were collected along with epidemiological and clinical data from suspected dengue patients who visited different hospitals in Swat and Mansehra district of Pakistan between May-November 2013 during a dengue outbreak.Samples were tested for the detection of viral nucleic acid by real-lime PCR.non structural protein-1(NS1antigen and IgM antibodies by ELISA.Results:Out of 323 cases with clinical dengue infection,304 were positive by one or more diagnostic parameter:201 samples were positive by real-time PCR,209 were positive by NS1 ELISA and 190 were positive by IgM antibodies.Sensitivities of real-time PCR and NS1 F.LISA were comparable for early diagnosis of dengue virus infection.IgM antibody detection assay was found useful for the diagnosis in the samples collected later than day 5 of onset.Conclusions:The use of real-lime PCR or detection of non stnictural protein NS 1 by ELISA followed by IgM antibodies detection can be recommended for early diagnosis of dengue virus infection with a high level of accuracy.     

第1、2代酶联免疫试剂检测重型病毒性肝炎患者抗-HCV结果的比较

目的 比较第1代和第2代酶联免疫(ELISA)检测试剂盒检测重型肝炎患者的抗-HCV阳性率。方法 1984～1990年期间住院的重型肝炎患者78例。治疗前留置血清使用美国Ortho公司的第1代酶联免疫检测试剂盒检测抗-HCV；1997～2003年期间住院的重型肝炎患者251例，于治疗前使用国产第2代酶联免疫检测试剂盒(厦门新创)检测抗-HCV。结果 使用第1代ELISA检测的抗-HCV阳性率为51．9％，使用第2代ELISA试剂检测的抗HCV阳性率为1．2％，两组比较，差异有显著性(x^2=133．68，P≤0．001)。结论 使用第2代ELISA试剂检测重型肝炎患者血清抗-HCV的阳性率明显低于第1代ELISA检测的阳性率。