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In late October 1991, an outbreak of gastroenteritis, following the consumption of raw oysters involving more than 200 people, was reported in five locations in Quebec, Canada. Bacteriological analysis of the oysters involved indicated low levels of fecal coliforms, but direct electron microscopy of stool samples obtained from two people involved in the outbreak revealed that both contained 27-34 nm, small, round Norwalk-like viruses. Immunoelectron microscopy, using acute sera obtained from these individuals and convalescent serum from another person related to the outbreak, revealed antibody coatings on these Norwalk-like viruses with all three sera. Solid-phase immunoelectron microscopy demonstrated that these viruses were also antigenically similar or related to a Norwalk-like virus isolated as the cause of a gastroenteritis outbreak in a home for the aged between December 1988 and January 1989 in Thunder Bay, Ontario. From these findings and the symptoms of the illness, the Norwalk-like virus was considered as the causal agent of the outbreak due to the consumption of contaminated oysters. How the oysters became contaminated was not determined. Oysters harvested from the areas initially thought to have been the origin of the implicated shellfish were tested for the presence of viral fecal indicators using tissue culture and electron microscopy with negative results. It is most likely that the implicated lot also contained oysters harvested from another area, also open, but which was downstream from an identified source of human fecal contamination.

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OBJECTIVE: To determine the prevalence of hepatitis B antigen (HBsAg), antibody to hepatitis C virus (anti-HCV), and antibody to human immunodeficiency virus (anti-HIV) among residents of a long-term care facility. DESIGN: Anonymous unlinked serosurvey. SETTING: Accredited university-affiliated long-term-care facility in Toronto with 300 chronic-care hospital patients, 350 nursing home residents, and 200 residents of a senior citizens' apartment complex. INTERVENTIONS: Sera from left-over blood samples obtained from residents in November 1990 were tested for HBsAg, anti-HCV, and anti-HIV using standard methods. RESULTS: A total of 508 sera were tested. The number (%) positive for HBsAg, anti-HCV, and anti-HIV, respectively were: 3(0.6%), 7(1.4%), and 0(0%). CONCLUSIONS: This is the first report defining rates of infection with bloodborne infective agents among residents of a long-term care facility. These results support the use of hepatitis B vaccine for medical and nursing staff and the implementation of universal precautions in long-term care facilities.

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Direct electron-microscopy (DEM), immune electron microscopy (IEM) and four different procedures of immune electron microscopy with colloidal gold immune complexes were evaluated for the detection of Norwalk-like virus and specific antibody. A solid-phase immune electron microscopy with colloidal gold immune complexes-triple layer method (SPIEMGIC-TLM) is developed for screening patients' specimens for the detection of Norwalk-like virus and its specific antibody. The method demonstrates low non-specific background labelling and is simple, sensitive and easy to perform. A quadruple layer method (SPIEMGIC-QLM), which is a modification of the triple layer method, has been established by adding a cross-linking anti-IgG layer to amplify the reaction and to provide a more sensitive test which is suitable for screening monoclonal antibodies prepared against 32-34-nm Norwalk-like virus isolated in our laboratory.

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From 100 cases of gastroenteritis among children caused by adenovirus infection in Ontario, 33 virus isolates were divided into three categories according to their biological behavior in tissue cultures. So far, the results of neutralization tests, structural protein analysis, and DNA restriction patterns showed that the virus of category 1 was similar to adenovirus type 40. However, the adenovirus of category 2 was a distinct adenovirus which shared some similarities with adenovirus type 5. Viruses of category 3 are still under investigation.

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Two ELISA systems for the detection of human rotaviruses were developed. In the first system antibodies to Nebraska calf diarrhea virus (NCDV) were used for coating the solid matrix and for the preparation of the enzyme conjugate. In the second system antibodies to human rotavirus and antibodies to simian rotavirus (SA11) were used for coating the solid matrix and for the preparation of the enzyme conjugate respectively. The second ELISA system proved to have a broader spectrum for the detection of human rotaviruses. By using the two ELISA systems, the different types of human rotavirus could be distinguished. The ELISA tests developed were 8 to 64 times as sensitive as electron microscopy (EM) and (or) counterimmunoelectrophoresis (CIEP). The antigen detected by ELISA was shown to be different from that detected by the hemagglutination test.

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An enzyme-linked immunosorbent assay (ELISA) was developed for the detection of antibodies to influenza A/Hong Kong/1/68, influenza A/Victoria/3/75, influenza B/Hong Kong/5/72, and parainfluenza type 1 viruses. Development and standardization of the method indicated that an acetone-ethyl alcohol mixture was a suitable fixative for the preparation of the solid-phase coupled antigen. The addition of sodium azide to the enzyme-conjugated solution and the concentrations of the enzyme-conjugate antiglobulin and test sera employed were all critical factors in the success of the ELISA procedure. The ELISA test was specific; there was no cross-reaction between influenza A and B or parainfluenza type 1 viruses. The concordance between ELISA and hemagglutination inhibition results suggested that both tests probably detected the same type of antibodies. The ELISA procedure was 8 to 64 times more sensitive than complement fixation and/or hemagglutination inhibition tests. Low levels of antibody in patients' sera were detected only by the ELISA test. During the course of the testing period false positive reactions were not encountered. The results of ELISA could be obtained within 3 h. The ELISA test required a very small amount of serum and, therefore, offered an opportunity to detect the presence of maternal antibodies to influenza viruses in blood collected from infants by heel prick.

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Highly purified Nebraska calf diarrhea virus (NCDV) was prepared by cesium chloride density gradient centrifugation. The effect of temperature, pH, different concentrations of formaldehyde, chloroform, ether, ethyl alcohol, and methyl alcohol on NCDV hemagglutinin and virus morphology was studied. NCDV hemagglutinin was inactivated by temperature, pH 2.0, chloroform, ethyl alcohol, and methyl alcohol.

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