One hundred and six patients suffering from severe dehydrating diarrhoea were studied of whom 36 patients were positive for Vibrio cholerae. Out of 36, 15 were positive for V. cholerae O1, 10 for V. cholerae O139 and 11 for V. cholerae non-O1 non-O139. O1 and O139 were positive for the 301-bp ctxA amplicon and 471-bp tcpA amplicon indicating that the strains possessed toxigenic capability whereas no non-O1 non-O139 strain possessed ctxA or tcpA genes. Post-admission severity of purging and amount of ORS required were less in the V. cholerae non-O1 non-O139 group (P<0·05) compared to the V. cholerae O1 and O139 groups. It appears from this study that a cholera-like clinical condition can be caused in the absence of CT as exemplified by strains of non-O1 non-O139.

The 1994 cholera epidemic in Guinea-Bissau resulted in 15878 reported cases and 306 deaths. Early in the epidemic, although the health ministry mandated that the bodies of persons dying of cholera be disinfected, outbreaks occurred in several villages following funerals in the region of Biombo. To determine the influence of disinfection and funeral activities on cholera transmission, we analysed surveillance data and conducted a case-control study following a funeral. The attack rate during the week following funerals was higher in villages where bodies were not disinfected (risk ratio = 2·6, 95% confidence interval [CI] 1·9–3·8). Cholera was strongly associated with eating at a funeral with a non-disinfected corpse (odds ratio [OR] = 14·5, 95% CI 0·9–786) and with touching (i.e., transporting, washing) the body (OR = 36·2, 95% CI 2·6–1769). During cholera epidemics, in addition to other cholera prevention activities, health officials should inform community leaders about the risk of cholera transmission during funerals, meals should not be served at funerals, and bodies of persons dying of cholera should be disinfected.

A 16-month old female child living on an Ontario dairy farm was taken to hospital suffering from bloody diarrhoea. Escherichia coli O157[ratio ]H7 was isolated from her stool. Initial tests of well water samples were negative for E. coli by standard methods but culture of selected coliform colonies on sorbitol-MacConkey agar led to isolation of E. coli O157[ratio ]H7. E. coli O157[ratio ]H7 was also isolated from 63% of cattle on the farm. The E. coli O157[ratio ]H7 isolates from the child, the water and the cattle were phage type 14, produced verotoxins 1 and 2, and were highly related on analysis by pulsed field gel electrophoresis. The child did not have known direct contact with the cattle and did not consume unpasteurized milk. Hydrogeological investigation revealed the design and location of the well would allow manure-contaminated surface water to flow into the well. This investigation demonstrates that cattle farm well water is a potential source of E. coli O157[ratio ]H7 which may not be identified by standard screening for E. coli in water.

To investigate if there is a reservoir of Escherichia coli O157 in Norwegian cattle, faecal samples from 197 cattle herds were screened for E. coli O157 by the use of immunomagnetic separation (IMS) and PCR during the 1995 grazing season. Six E. coli O157[ratio ]H-isolates were detected in two herds, one isolate in one and five in the other. The isolates carried the stx1, stx2, and eae genes, and a 90 MDa virulence plasmid. They were toxinogenic in a Vero cell assay. From 57 other herds, 137 faecal samples were positive for stx1 and/or stx2 genes detected by PCR run directly on IMS-isolated material. Among these samples, stx2 were the most widely distributed toxin encoding genes. No difference was found among milking cows and heifers in the rate of stx1 and/or stx2 in positive samples.

In September 1994, a complaint was registered at a public health unit concerning a cheese product. In addition, public health laboratories in Ontario reported an increase in the number of isolates of Salmonella berta from patients with diarrhoeal illness. A clinical, environmental and laboratory investigation was initiated to determine the nature of this outbreak. Isolates of Salmonella berta were compared using large fragment genomic fingerprinting by pulsed-field gel electrophoresis (PFGE). By late October, 82 clinical cases had been identified including 35 confirmed, 44 suspected and 3 secondary. The investigation linked illness to consumption of an unpasteurized soft cheese product produced on a farm and sold at farmers' markets. Subtyping results of patient, cheese and chicken isolates were indistinguishable, suggesting that the cheese was contaminated by chicken carcasses during production. The outbreak illustrates the potential role of uninspected home-based food producers and of cross-contamination in the transmission of foodborne bacterial pathogens.

Public health surveillance requires the monitoring of waterborne disease, but sensitive and specific detection of relevant incidents is difficult.

The Communicable Disease Surveillance Centre receives information from various sources about clusters of cases of illness in England and Wales. The reporter may suspect that water consumption or recreational water exposure is the route of infection, or subsequent investigation may raise the hypothesis that water is associated with illness.

It is difficult to prove beyond reasonable doubt that such a hypothesis is correct. Water samples from the time of exposure are seldom available, some organisms are difficult to detect and almost everyone has some exposure to water. Therefore, we have developed a method of categorizing the degree of evidence used to implicate water. The categories take into account the epidemiology, microbiology and water quality information. Thus outbreaks are classified as being associated with water either ‘strongly’, ‘probably’ or ‘possibly’.

This system allows a broad database for monitoring possible effects of water and is not confined to the few outbreaks which have been intensively investigated or have positive environmental microbiology. Thus, for reported incidents, the sensitivity of classifying it as water associated should be high but this may be at the expense of specificity, especially with the ‘possible’ association.

Following the 1993 Milwaukee cryptosporidiosis outbreak, we examined data from eight sources available during the time of the outbreak. Although there was a remarkable temporal correspondence of surveillance peaks, the most timely data involved use of systems in which personnel with existing close ties to public health programmes perceived the importance of providing information despite workload constraints associated with an outbreak. During the investigation, surveillance systems which could be easily linked with laboratory data, were flexible in adding new variables, and which demonstrated low baseline variability were most useful. Geographically fixed nursing home residents served as an ideal population with non-confounded exposures. Use of surrogate measurements of morbidity can trigger worthwhile public health responses in advance of laboratory-confirmed diagnosis and help reduce total morbidity associated with an outbreak. This report describes the relative strengths and weaknesses of these surveillance methods for community-wide waterborne illness detection and their application in outbreak decision making.

This paper describes 2 outbreaks of hepatitis A infection in Finland, a very low endemic area of hepatitis A infection, where a large proportion of the population is now susceptible to infection by hepatitis A virus (HAV). The first outbreak involved people attending several schools and day-care centres; the second employees of several bank branches in a different city. The initial investigation revealed that both were related to food distributed widely from separate central kitchens. Two separate case-control studies implicated imported salad food items as the most likely vehicle of infection. HAV was detected in the stool of cases from both outbreaks using reverse-transcriptase polymerase chain reaction; however, comparison of viral genome sequences proved that the viruses were of different origin and hence the outbreaks, although occurring simultaneously, were not linked. Foodborne outbreaks of HAV may represent an increasing problem in populations not immune to HAV.

Four Swedish strains of equine H3N8 influenza virus isolated from outbreaks during the last 4 years were characterized. Antigenic typing using monoclonal antibodies raised against a variety of H3N8 strains showed that the viruses are heterogeneous, the 1993 isolate being closely related to the 1991 Swedish isolate TAB/91 and the other three isolates from 1994 and 1996 being more closely related to each other. This pattern is reflected in the phylogenetic data calculated from nucleotide sequencing of the haemagglutinin genes. H3N8 equine influenza can be seen to be evolving in two distinct lineages, one European and one American. The 1993 isolate is closely related to the European lineage and is the most recent Swedish strain of this lineage to be isolated. The 1994 and 1996 isolates fit into the American lineage, which contains recent isolates from the United States and also Britain. These results indicate that American-type H3N8 viruses have become endemic in Sweden and, in light of the antigenic differences which can be observed between viruses belonging to the two lineages, we believe that equine influenza virus vaccines should be updated with an American-type virus strain.

A retrospective cohort study was conducted to quantitate the relationship between neutropenia and rates of clinical bacteraemia among adults with HIV infection receiving medical care at one institution between 1991–5. The primary exposure, absolute neutrophil count (ANC), was summarized as mean ANC within a given week, using a five-level stratification (reference > 1000/μl). ANC stratum-specific rates of bacteraemia were calculated, by organism type. Linear trend tests were performed to assess dose-response relationship between neutropenia and rates of bacteraemia. The cohort included 1645 patients contributing 26785 patients-weeks and 191 episodes of bacteraemia. The unadjusted effect of neutropenia was most evident for bacteraemia due to E. coli (RR 3.4), Klebsiella pneumoniae (RR 16·7), and P. aeruginosa (RR 10.4). For bacteraemia due to any of these three organisms (47 episodes), with reference ANC > 1000/μl, relative rates were: 751–1000/μl, 1·12; 501–750/μl, 2.11; 251–500/μl, 13·58; 0–250/μl, 21·89.

Parasitic infections have been reported to be relatively common among the Southeast Asian labourers in Taiwan. This study, conducted in 1992–6, was designed to determine the temporal changes of the prevalence. Faecal specimens were examined by the formalin-ethyl acetate sedimentation technique and blood samples screened using the quantitative buffy coat technique and confirmed by Giemsa stained blood smear. The overall prevalence of intestinal parasitic infections was 10·3%. The annual prevalence decreased from 33·3% in 1992–3 to 4·6% in 1995–6. The Thai (12·0%) and Indonesian (11·1%) had a higher prevalence than the Malaysian (6·7%) and Filipinos (5·9%). Opisthorchis viverrini was the most important parasite in the Thai and Trichuris trichiura in the remaining groups. Moreover, no blood parasites were found in the labourers. The dramatic temporal decline in the intestinal parasitic infections suggests that limiting the entry of infected persons, periodic follow-ups, and immediate treatment of sporadic cases are necessary in preventing transmission of non-indigenous parasites through large population change.

During one year from June 1992 serum IgG antibodies to Toxoplasma gondii among 35940 pregnant women were measured in a cross-sectional study conducted in Norway. The overall prevalence was 10·9%. The lowest prevalences were detected in the north (6·7%) and in the inland counties (8·2%). A significantly higher prevalence was detected in the southern counties (13·4%) where a mild, coastal climate prevails. Women with foreign names had a higher prevalence (22·6%) than women with Norwegian names (10·0%). The high prevalence among women living in the capital city (Oslo) as compared to other cities and rural areas (13·2% vs. 10·1% and 10·2% respectively), was explained by the higher proportion of foreign women in Oslo. Prevalence significantly increased with age in women over 34 years old. This increase was only detected among women with Norwegian names. An increase in prevalence according to number of children was detected. Women without children had a prevalence of 8·8% while women with three children or more had a prevalence of 14·9%. Multivariate analyses showed that being seropositive was independently associated with county of residence, age, nationality and number of children.

To test the hypothesis that chronic infection with Chlamydia pneumoniae, Helicobacter pylori or cytomegalovirus is associated with coronary heart disease risk in elderly men, a nested case-control study in a cohort investigated in 1985 and 1990 in the town of Zutphen, The Netherlands, was designed. Fifty-four cases with a first diagnosed coronary event between 1985 and 1990, and 108 age-matched control subjects free of coronary heart disease during follow up were included in the study. The overall prevalence of antibodies to cytomegalovirus was 74·7%, to H. pylori 75·9% and to C. pneumoniae 84·0%. A high level of antibodies to C. pneumoniae was associated with an increased coronary heart disease risk (OR=2·76; 95% CI=1·31–5·81). This association was stronger in cases developing both myocardial infarction and angina pectoris, than in cases developing only one of these. This association was independent of potential confounders. Antibodies to cytomegalovirus or H. pylori were not associated with coronary heart disease risk. These results support the hypothesis of a role of chronic C. pneumoniae infections in the immunopathogenesis of atherosclerosis.

Over a period of 40 months, 4374 foxes were randomly sampled from an area located in northwestern Brandenburg, Germany, and examined parasitologically for infections with Echinococcus multilocularis. Spatial analysis of the origin of infected animals identified two (one central and one southeastern) high-endemic foci with an estimated prevalence of 23·8%. By contrast, a prevalence of 4·9% was found in the remaining (low-endemic) area. The prevalences among juvenile and adult foxes were compared in the high-endemic and the low-endemic areas. To analyse the central high-endemic focus further, the random sample was stratified by zones representing concentric circles with a radius of 13 km (zone 1) or xn−1+7 km for the remaining three zones from the apparent centre of this focus (anchor point). Prevalences calculated for each zone showed a decrease from zone 1 (18·8%) to zone 4 (2·4%) with significant differences for all zones but zones 3 and 4. The relative risk of an infection decreased rapidly in a distance range of 26 km around the high-endemic focus, whereas the relative risk remained unchanged within a distance of 5 km around the anchor point. The importance of heterogeneous spatial distribution patterns for the diagnosis and epidemiology of the infection is discussed.