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Detection and analysis of a small round-structured virus strain in oysters implicated in an outbreak of acute gastroenteritis.

Outbreaks of shellfish-transmitted viral disease occur periodically, but frequently the causative agent is not identified. In November 1993, during investigation of a multistate outbreak of acute gastroenteritis, incriminated lots of oysters were collected. Oyster tissues (stomachs and digestive diverticula) were processed for virus extraction and nucleic acid purification. Human calicivirus sequences were sought by reverse transcriptase PCR using different primer sets. Amplicons were obtained from 9 of 10 shellfish samples from four different lots when primers specific for the outbreak virus strain were used. The specificity of the amplification was confirmed by hybridization. The amplicons from the nine positive oysters were cloned and sequenced. The sequence of each of the clones was identical to the others but showed some variation (7 of 81 bp) from the sequences obtained from the stools of three persons made III by the outbreak.

Animals↗

Homologous versus heterologous immune responses to Norwalk-like viruses among crew members after acute gastroenteritis outbreaks on 2 US Navy vessels.

Host immune responses to human caliciviruses are difficult to study because of the lack of a clear definition of antigenic or serological types. This report describes antibody responses to several Norwalk-like viruses in large outbreaks of acute gastroenteritis on 2 US Navy ships. Enzyme immunoassays (EIAs) were used to measure antibody responses. To understand the antibody response to a homologous strain causing the outbreaks, the viral capsid gene of one isolate (C59) was expressed in baculovirus and included in the EIAs. Significantly greater seroresponses were detected in patients against the homologous strain than against the heterologous strains. Strains within genogroups reacted more strongly than did strains between genogroups. Significantly higher antibody titers against the outbreak strain were detected in acute serum samples from control subjects than in those from case patients. These results indicate that recombinant EIAs are useful for outbreak investigation and that the homologous antibody might be protective against reinfection.

Acute Disease↗

Prevalence of small round structured virus infections in acute gastroenteritis outbreaks in Tokyo.

During the three-year period from 1984 to 1987, 506 acute gastroenteritis outbreaks involving 14,383 patients were reported to the Bureau of Public Health, Tokyo Metropolitan Government. Eighty (4,324 patients) of 150 outbreaks (4,860 patients) from which etiologic agents were not identified were subjected to virological investigation. Spherical particles of 28-32 nm in diameter with capsomere-like structures on the surface were detected in patients' stool specimens. Buoyant density of the particles appeared to be 1.36 to 1.40 g/ml in CsCl. Seroconversion to the particles was observed in patients by immune electron microscopy. From these observations, we concluded that the detected particles were members of small round structured virus (SRSV), and that they were implicated in the etiologically ill-defined outbreaks encountered. Prevalence of SRSV infections in these outbreaks was examined by electron microscopy. SRSV was positive in 83.8% of the outbreaks, and 96.4% of the cases. SRSV-positive outbreaks usually occurred during winter in contrast to bacterial outbreaks which often occurred in the summer season. Of 80 outbreaks examined, 53 were associated with the ingestion of oysters, and the remaining 27 mostly with food other than oysters. Oyster-associated outbreaks usually occurred on a small scale, while unassociated ones on diverse scales ranged from family clusters to large outbreaks.

Acute Disease↗

Rotavirus serotype G9P[8] and acute gastroenteritis outbreak in children, Northern Australia.

During 2001, an outbreak of severe acute gastroenteritis swept through Central and northern Australia and caused serious disruption to health services. We tracked and characterized the rotavirus strain implicated in the outbreak. Comparison of the electropherotypes of outbreak samples suggested that one G9P[8] strain was likely responsible for the outbreak. Samples were obtained from geographically distinct regions of Australia where the epidemic had occurred. The outbreak strains showed identical nucleotide sequences in genes encoding three rotavirus proteins, VP7, VP8, and NSP4, but they were distinct from G9P[8] strains isolated in previous years. Several of the amino acid substitutions on the VP7 and NSP4 proteins were identified in regions known to influence function and may have contributed to the emergence and increased dominance of the outbreak strains. Rotavirus serotype surveillance should continue with methods capable of identifying new and emerging types.

Antigens, Viral↗

Western blot (immunoblot) assay of small, round-structured virus associated with an acute gastroenteritis outbreak in Tokyo.

Small, round-structured virus (SRSV) was detected in a stool specimen of a patient during an acute gastroenteritis outbreak in Tokyo and was tentatively named SRSV-9. SRSV-9 was purified by sucrose velocity gradient centrifugation after CsCl density gradient centrifugation. The buoyant density of SRSV-9 appeared to be 1.36 g/ml in CsCl. A Western blot (immunoblot) assay using the biotin-avidin system revealed that SRSV-9 was antigenically related to the Hawaii agent but distinct from the Norwalk agent and contained a single major structural protein with a molecular size of 63.0 +/- 0.6 kilodaltons. The prevalence of SRSV-9 infection in Tokyo was surveyed by the Western blot antibody assay by using a crude virus preparation as the antigen. Seroconversion was observed in 56.5% of the patients involved in the outbreaks from which SRSV was detected by electron microscopy.

Acute Disease↗

Genomic characteristics and tracing analysis of an acute gastroenteritis outbreak associated with rotavirus C in a boarding high school.

BACKGROUND: Rotaviruses are major pathogens of childhood acute gastroenteritis, dominated by rotavirus A (RVA). Outbreaks caused by human rotavirus C (RVC) are rarely reported, and relevant genomic data remain scarce. This genomic investigation of an RVC outbreak improves our understanding of viral diversity and transmission dynamics. METHODS: We performed epidemiological surveys, nucleic acid testing and whole-genome sequencing (WGS) on specimens from a 2025 RVC-associated gastroenteritis outbreak at a Chinese boarding high school. Sequence alignment, phylogenetic and molecular tracing analyses were conducted to explore RVC evolution via point mutation, segment reassortment and genomic recombination. RESULTS: This typical point-source campus outbreak was linked to an indoor student gathering matching the incubation period of RVC. Thirteen RVC FX strains were recovered from 11 rectal swabs and two vomitus samples. Their viral protein (VP) 4 and VP7 sequences shared high homology with Russian reference strains, carrying distinct amino acid variations. No segment reassortment or recombination was detected in VP4/VP7 genes. CONCLUSIONS: Dense, closed campus settings facilitate RVC clustered transmission. Limitations included absent screening of asymptomatic canteen staff. Rapid nucleic acid testing enabled timely pathogen identification for outbreak control. Greater attention should be paid to the public health risk of RVC. These whole-genome sequencing data enrich resources for studying RVC evolution and vaccine development.

Acute gastroenteritis outbreak↗

Epidemiology of acute gastroenteritis outbreaks caused by Noroviruses in Okayama, Japan.

Noroviruses (called formerly "Norwalk-like viruses") cause food-borne gastroenteritis outbreaks. These outbreaks were thought to be related to shellfish consumption, although non-shellfish related outbreaks also occurred frequently in Japan. To clarify the epidemiology of Norovirus outbreaks, 435 stool samples were collected from 60 acute non-bacterial gastroenteritis outbreaks occurring over 8 years in Okayama, Japan. Using reverse transcription-PCR (RT-PCR), Noroviruses were detected in 257 cases (59.1% of all samples) from 46 outbreaks (77% of all outbreaks). The majority of the 46 Norovirus outbreaks (89%) occurred during November to March; notably one-third occurred in December. Restaurants, schools, and welfare institutions accounted for the major settings in 50%, 20%, and 15% of the Norovirus outbreaks, respectively. This was similar to other reports from Japan, but differed from those from the United Kingdom. The transmission routes were assigned in 27 of the Norovirus outbreaks. In 18 outbreaks the routes were related to human contact (7 from food handlers and 11 from person-to-person contact), whereas those related directly to shellfish occurred only in 9 outbreaks. These results suggest that transmission routes related to human contact are more important than recognized previously in the context of preventive medicine. Furthermore, all outbreaks in which some of the samples contained dual genogroups of Noroviruses were related to shellfish, suggesting that consumption of contaminated shellfish frequently results in mixed Norovirus infections in contrast to other transmission routes and that coexistence of genogroups is a useful marker for shellfish-related outbreaks.

Adolescent↗

Molecular analysis of noroviruses involved in acute gastroenteritis outbreaks in military units in Israel, 1999-2004.

The study presented here was conducted to determine the genetic properties of noroviruses (NoVs) identified between 1999 and 2004 in army recruits with acute gastroenteritis. Partial sequence analysis of the RNA-dependent RNA polymerase gene revealed the presence of two major sub-genogroups, all of which were related to genogroup II of NoV. Serological analysis using recombinant antigens confirmed this observation. Local strains associated with a 1999 outbreak were closely related to GII-6 strains, while those identified later were very closely related to GII-4 strains. GII-4 strains were also associated with an outbreak in civilian nursing homes in Israel in 2002 and samples from this outbreak were included in this study for comparison. This is the first report describing the molecular properties of NoV strains associated with diarrhea-related morbidity in Israel.

Acute Disease↗

Molecular detection and sequence analysis of human caliciviruses from acute gastroenteritis outbreaks in Hungary.

Three viral gastroenteritis (VGE) outbreaks that occurred in 1998-1999, in Hungary were investigated for the presence of human caliciviruses (HuCVs). HuCVs in stool specimens were detected by reverse transcription-polymerase chain reaction (RT-PCR) using primer pair 289/290, which was designed based on the RNA-dependent RNA polymerase (RdRp) sequence. RT-PCR results were confirmed by sequencing showing that all three outbreak strains belonged to genogroup II of "Norwalk-like viruses" (NLVs). Two strains had high sequence identity with strains in known genetic clusters (Hawaii and Lordsdale clusters). The third strain (MOH) had distinct RdRp sequence, sharing 77/86% (nt/aa) identity with Snow Mountain virus (SMV), the closest genogroup II virus. To characterize MOH further, we cloned, sequenced, and expressed in baculovirus its capsid gene. It had 75/79% (nt/aa) identity with SMV, but 97/98% (nt/aa) identity with NLV/Hillingdon/90/UK, a recently identified genetic cluster of HuCVs. The recombinant MOH (rMOH) capsid protein self-assembled into virus-like particles (VLPs), which is antigenically distinct from other recombinant HuCV capsid antigens available in our laboratory. Further study of this VLP will have important applications in antigenic characterization and diagnosis of HuCVs.

Acute Disease↗

Small, round-structured viruses (SRSVs) associated with acute gastroenteritis outbreaks in Gifu, Japan.

Two outbreaks of non-bacterial gastroenteritis occurred in Gifu prefecture in January 1989 and in January 1991. Both outbreaks were closely related to the consumption of raw oysters, and showed similar clinical features. Small, round-structured virus particles were found in patient stools in both outbreaks by electron microscopy. The role of these particles as the causative agents of the outbreaks were strongly suggested by immune electron microscopy and/or western-blotting immunoassay. When compared with SRSV-9 (Tokyo/SRSV/86-510) reported previously (Hayashi et al, J. Clin. Microbiol., 27: 1728-1733, 1989), it was found that these viral particles were antigenically similar to SRSV-9, and had a major structural protein of 63 kilodaltons (kDa). Further, the prevalence of this agent in Gifu area was examined by western blot antibody assay using 67 serum samples collected from the inhabitants in 1991. The results indicated the circulation of the same or antigenically similar agent in this area.

Adult↗

[Practical lessons from the risk management of an outbreak of acute gastroenteritis in a public school].

We present our reflections on the management of an acute gastroenteritis outbreak in a public school, which caused a public health crisis, and the conclusions drawn from this experience. The methodology of strengths, weaknesses, opportunities, and threats (SWOT) analysis was used. This article describes the epidemiology of the incident and the policy decisions made, but focuses on operational aspects of outbreak management. The experience of the outbreak control team, liaison with other organizations, and data management are discussed. The difficulties encountered by the outbreak team related to delay in declaring in the outbreak, lack of training in some of the entities involved, and incorrect use of the surveillance circuits. Current protocols and specific action plans for the management of outbreaks should be improved through self-evaluation and updating of resources and knowledge.

Acute Disease↗

[Nosocomial epidemic outbreak of acute gastroenteritis by Norwalk-like virus].

BACKGROUND: From the notification of an acute gastroenteritis outbreak in a nursing home, an epidemiological study was started to determine the characteristics of the outbreak and its spreading pattern and to identify determining factors. PATIENTS AND METHOD: A study of historic cohorts was performed and the case was defined by the presence of diarrhea and vomiting. Spatial aggregation in double rooms was analyzed by a binomial distribution and temporal aggregation was analyzed by a relative risks model. The variables in the study allowed us to calculate the adjusted relative risk; the odds ratio was calculated in relation to the meal on day January 30. RESULTS: We studied 95.9% residents. The total attack rate was 28.7% (31.8% employees, 30.1% permanent residents and 15.2% day residents). The attack rate in rotation health personnel was 45.2%. Spatial and temporal spread in double rooms was negative. There was a significant association with the disease in rotator employees (RR = 3.22; CI 95%, 1.30-7.99; p = 0.02). No association was found between eating and disease (OR = 1.5; CI 95%, 0.4-6.1; p = 0.46). Norwalk-like virus was isolated in four faecal samples. CONCLUSIONS: This epidemic outbreak had the characteristic of a nosocomial infection with a likely person-to-person transmission mechanism. The main factor contributing to the spread of the infection was the existence of employees in permanent contact with residents with an important physical and mental impairment, hence highly dependent on the care provided by these health workers.

Acute Disease↗

The frequency of a Norwalk-like pattern of illness in outbreaks of acute gastroenteritis.

Records of 642 outbreaks of acute gastroenteritis were reviewed to determine the proportion of outbreaks that were clinically and epidemiologically consistent with Norwalk-like virus infection. Using as our criteria stool cultures negative for bacterial pathogens, mean (or median) duration of illness 12-60 hours, vomiting in greater than or equal to 50 per cent of cases, and, if known, mean (or median) incubation period of 24-48 hours, we found that 23 per cent of waterborne outbreaks, 4 per cent of foodborne outbreaks, and 67 per cent, 60 per cent, and 28 per cent of outbreaks in nursing homes, in summer camps, and on cruise ships, respectively, satisfied the criteria for Norwalk-like pattern. Of 54 outbreaks that satisfied the criteria for Norwalk-like pattern, 14 were investigated for virus etiology. Ten of these (71 per cent) yielded serologic evidence of Norwalk-like virus infection. Norwalk-like viruses are probably an important cause of outbreaks of acute gastroenteritis. Investigation for Norwalk virus antibody in outbreaks that are clinically and epidemiologically consistent with Norwalk-like virus infection is likely to yield diagnostically useful results.

Acute Disease↗

Epidemiology of Norwalk gastroenteritis and the role of Norwalk virus in outbreaks of acute nonbacterial gastroenteritis.

Outbreaks of Norwalk gastroenteritis, which may involve persons of all ages, occur during all seasons and in various locations. Waterborne, foodborne, and person-to-person modes of transmission have been described, and secondary person-to-person transmission is common. Outbreaks generally end in about 1 week; longer outbreaks occur only when new groups of susceptible persons are introduced, usually in the setting of a persistent common source of infection. The illness is generally mild and characterized by nausea, vomiting, diarrhea, and abdominal cramps. Vomiting is the predominant symptom among children, whereas diarrhea is commoner among adults. Forty-two percent of 74 outbreaks of acute nonbacterial gastroenteritis investigated by the Centers for Disease Control from 1976 to 1980 were attributed to the Norwalk virus. The rest resembled Norwalk outbreaks clinically and epidemiologically and were probably caused by 27-nm viral agents similar to the Norwalk virus.

Acute Disease↗

The 33- to 39-nm virus-like particles, tentatively designed as Sapporo agent, associated with an outbreak of acute gastroenteritis.

An outbreak of nonbacterial gastroenteritis occurred in an orphanage in December 1979. Of 54 residents, 43 were affected with acute gastroenteritis. Diarrhea was the commonest symptom. The 33- to 39-nm virus-like particles, tentatively designated as Sapporo agent, were detected in 17 (48.6%) of the patients' 35 fecal specimens. Morphologically, it was difficult to distinguish the Sapporo agent from other agents without geometrical pattern of the surface. Antigenically, the Sapporo agent related to the Otofuke agent detected in an outbreak of the institution for mentally retarded adults and also to the SRV ;76 detected in familial cases of infectious gastroenteritis. The Sapporo agent might belong to a new group of those gastroenteritis viruses which were larger in size than the Norwalk virus group.

Antibodies, Viral↗

Calicivirus detected in outbreaks of acute gastroenteritis in school children.

Outbreaks of acute gastroenteritis occurred in AK and N Primary Schools of Osaka Prefecture early in March and early in November, respectively, 1977. Epidemiological surveys were carried out in both schools with the following results. The morbidity rates were 21.8% (AK) and 8.5% (N) among all pupils, and 41.7% (AK) and 36.8% (N) in special age groups. The main clinical symptoms were abdominal pain (77.2-91.3%), diarrhea (38.4-41.3%) and vomiting (6.5-41.6%). Electron microscopic observations of negatively stained specimens showed that five of 15 fecal extracts obtained from patients in the two schools contained virus particles of 35-40 nm diameter with some black hollows on the surface of complete particles and ten projection-like structures at the edge of empty shells. These morphological characteristics resemble those of calicivirus particles. Immune electron microscopic examination suggested that outbreak in AK School was associated with this virus. Attempts to cultivate the viruses in various cultured cells and in suckling mice were unsuccessful.

Antibodies, Viral↗

Virus-like particle, 35 to 40 nm, associated with an institutional outbreak of acute gastroenteritis in adults.

In an outbreak of acute gastroenteritis in an institution for the mentally retarded at Otofuke, Hokkaido, Japan, virus-like particles were observed by electron microscopy in five of seven stool specimens from the patients. The particles had 10 rod-shaped and 10 round projections or capsomeres on the periphery, measured 35 to 40 nm in diameter, and had a buoyant density of 1.35 to 1.37 g/ml in cesium chloride. Attempts to culture these particles in tissue culture or in mouse brain were unsuccessful. Immune electron miscroscopy performed with the virus from the patients as antigen demonstrated significant serological responses in all patients examined. Antigenic similarity of the virus particles obtained from five patients was also confirmed by immune electron microscopy with the paired acute- and convalescent-phase sera of one of the patients. Furthermore, in immune electron micrsocopy these particles appeared to have no antigenic relationship to three candidate viruses for gastroenteritis so far reported: the Norwalk agent, the W agent, and the calicivirus-like particle. These results suggested the possibility that this agent, tentatively designated as the Otofuke agent, might be a new candidate virus for gastroenteritis.

Acute Disease↗