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Prevalence of small round structured virus infections in acute gastroenteritis outbreaks in Tokyo
1Department of Microbiology, Tokyo Metropolitan Research Laboratory of Public Health.
Abstract:
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.
Insights
Small round structured virus (SRSV) caused many unexplained gastroenteritis outbreaks in Tokyo. These viruses were frequently linked to oyster consumption and winter seasonality, highlighting their public health impact.
Area of Science:
- Virology
- Public Health
- Epidemiology
Background:
- Acute gastroenteritis outbreaks pose a significant public health challenge.
- Etiologic agents for many gastroenteritis outbreaks remain unidentified.
Purpose of the Study:
- To investigate the cause of unexplained acute gastroenteritis outbreaks in Tokyo.
- To identify the prevalence and characteristics of small round structured viruses (SRSV) in these outbreaks.
Main Methods:
- Virological investigation of stool specimens from patients in unexplained outbreaks.
- Detection and characterization of viral particles using electron microscopy and buoyant density analysis.
- Serological testing to confirm patient immune response to detected viruses.
Main Results:
- Small round structured viruses (SRSV), 28-32 nm in diameter, were identified in patients' stool.
- SRSV were implicated in 83.8% of examined outbreaks and 96.4% of cases.
- SRSV outbreaks predominantly occurred in winter and were often associated with oyster consumption.
Conclusions:
- SRSV are a major cause of acute gastroenteritis outbreaks previously lacking an identified etiology.
- Oyster-associated outbreaks are typically small-scale, while non-oyster-associated outbreaks vary in size.
- Understanding SRSV seasonality and transmission routes is crucial for public health interventions.