A large outbreak of campylobacteriosis associated with a municipal water supply in Finland

In August 1998, an outbreak of campylobacteriosis occurred in one municipality in northern Finland. A 10% random sample of residents (population 15 000) was selected through the National Population Registry for a survey conducted by using postal questionnaires. Cases were defined as residents of the municipality with onset of acute gastroenteritis from 1 to 20 August 1998. Of 1167 respondents (response rate 78%), 218 (18.7%) met the case definition. Drinking non-chlorinated municipal tap water was strongly associated with illness (OR 34.4). The estimated total number of ill persons was 2700. Campylobacter jejuni was isolated from stool samples of 45 (61%) out of 74 patients tested. All five isolates tested had indistinguishable PFGE patterns. Water samples were negative for campylobacter and coliforms. Epidemiological and environmental evidence suggested mains repair as the source of contamination. Non-chlorinated ground-water systems may be susceptible to contamination and can cause large outbreaks.     

Contaminated drinking water in one town manifesting as an outbreak of cryptosporidiosis in another

In early 1992 we identified an outbreak of cryptosporidiosis in Oregon and sought to identify and control its source. We used a series of studies to identify risk factors for illness: (i) a case-control study among employees of a long-term-care facility (LTCF); (ii) a matched case-control study of the general community; (iii) a cohort study of wedding attendees; and (iv) a cross-sectional survey of the general community. Drinking Talent water was associated with illness in the LTCF (OR = 22.7, 95 % CI = 2.7-1009.0), and in the community (matched OR = 9.5, 95% CI 2.3-84.1). Drinking Talent water was associated with illness only among non-Talent residents who attended the wedding (P < 0.001) and in the community (RR = 6.5, 95 % CI 3.3-12.9). The outbreak was caused by contaminated municipal water from Talent in the absence of a discernible outbreak among Talent residents, suggesting persons exposed to contaminated water may develop immunity to cryptosporidiosis.     

Epidemiologic application of pulsed-field gel electrophoresis to an outbreak of Campylobacter jejuni in an Austrian youth centre

We report the first documented Campylobacter jejuni outbreak in an Austrian youth centre. Sixty-four children were involved of which 38 showed classical signs of campylobacter gastroenteritis. Since unpasteurized milk distributed by a local dairy was suspected to be the source of infection, stool samples were collected from 20 cows providing the milk. Five of the cows tested positive for C. jejuni. These isolates together with 37 clinical samples were compared by pulsed-field-gel electrophoresis (PFGE). The PFGE patterns, using the restriction endonucleases SmaI and SalI, were identical for the human and bovine isolates.This finding confirmed that the outbreak was caused by the consumption of unpasteurized milk contaminated with C. jejuni.     

Long-lasting Campylobacter jejuni contamination of milk associated with gastrointestinal illness in a farming family

This report describes an outbreak of gastroenteritis of 5 months' duration in a farming family, associated with the consumption of unpasteurized cows' milk, where Campylobacter jejuni was implicated. A total of six individuals in the family acquired the illness, and two had several episodes of diarrhoea within the 5-month period. Identical PFGE genotypes of C. jejuni were isolated from human and bovine faeces, and bulk tank milk samples. Incompletely sealed rubber liners fitted to a milking machine shortly before the outbreak started was the probable reason, allowing faecal material to contaminate the milk over the period concerned.     

Escherichia coli O157:H7 outbreak associated with consumption of ground beef, June-July 2002

OBJECTIVE: A case-control and environmental study tested the hypothesis that purchasing and eating ground beef from a specific source was the cause of a cluster of cases of hemolytic uremic syndrome (HUS) and Escherichia coli (E. coli) O157:H7 gastroenteritis. METHODS: A case-control study comparing risk factors was conducted over the telephone on nine case-patients with 23 selected controls. An environmental investigation was conducted that consisted of reviewing beef handling practices at a specific local supermarket and obtaining ground beef samples from the store and two households with case-patients. RESULTS: The analysis of the case-control study showed that eight case-patients (89%) purchased ground beef at Grocery Chain A compared with four controls who did not develop illness (17%) (matched odds ratio=undefined; 95% confidence interval 2.8, infinity; p=0.006). The environmental investigation showed that Grocery Chain A received meat from Meatpacker A. Laboratory analysis of meat samples from Meatpacker A and Grocery Chain A and stool samples from some patients recovered an identical strain of E. coli O157:H7 according to pulse-field gel electrophoresis. CONCLUSIONS: Both the case-control and environmental studies showed that purchasing ground beef at Grocery Chain A, which received ground beef from Meatpacker A, was the major risk factor for illness in eight case-patients; the ninth case-patient was found to be unrelated to the outbreak. Furthermore, meat from Meatpacker A was associated with a nationwide outbreak of E. coli O157:H7 illness that resulted in the second largest recall of beef in U.S. history at the time.     

Incidence of gastroenteritis in Norway--a population-based survey

In 1999-2000 we conducted a one-year, retrospective population-based survey in Norway to estimate the incidence of gastroenteritis and study the association with selected exposures. A self-administered questionnaire was mailed to 3000 persons selected at random from the population registry, with 250 persons being contacted each month. The response rate was 61%. The incidence of acute gastroenteritis was 1.2 per person-year. The incidence was higher for women than for men. Of the total of 171 cases, 29 (17%) consulted a physician, 13 (8%) reported that a stool sample was taken, and 7 (4%) were admitted to hospital. Among children aged less than 15 years, drinking water from a private water supply was associated with illness, while using chlorinated water was protective. Among adults aged 20-40 years, travelling abroad was associated with illness. The incidence in our survey is similar to rates found by FoodNet in United States.     

Case-control study of waterborne giardiasis in Reno, Nevada

An outbreak of Giardia lamblia gastroenteritis occurred in Reno, Nevada, in 1982, during which 324 laboratory-confirmed infections were reported. During the outbreak, Reno was supplied in part by surface water that was chemically coagulated, settled, and chlorinated, but was not filtered. Giardia cysts were recovered from the water supply, and a beaver infected with Giardia was found in one of the reservoirs. A case-control study indicated that, during the outbreak but not afterwards, persons with giardiasis drank more municipal water than did controls. Corrective measures, which included removing the infected beaver and increasing the chlorine concentration, were followed by a rapid decrease in reports of giardiasis.     

A foodborne outbreak of Campylobacter jejuni (O:33) infection associated with tuna salad: a rare strain in an unusual vehicle.

We report a foodborne outbreak of Campylobacter jejuni infection in a summer camp. Outbreak-related cases occurred in 79 persons including 3 secondary cases in campers. Campylobacter jejuni was isolated from stool specimens from 16 of 21 patients who submitted a sample; 13 viable isolates were serotyped and all were serotype O:33 (somatic O scheme) or HL:18 (heat-labile scheme), and biotype III (Lior scheme). This serotype is widely distributed geographically but rarely isolated from humans. Samples of water from the wells supplying the camp were negative for faecal coliforms, and raw milk had not been served in the camp. A matched (1:1) case-control study identified tuna salad served for lunch on 19 July as the likely food item associated with illness (matched odds ratio=22; 95% confidence intervals (CI)=3.6-908). Swimming in the camp pool and other recreational water use in area lakes by the campers were not statistically associated with illness. The precise mechanism of introduction of the organism into the tuna salad remains unknown; contamination most likely occurred through cross-contamination with another food product, the hands of a food handler, or a work surface. Several deficiencies in the operation of the camp kitchen were identified. In Wisconsin, kitchens of such camps are subject to different inspection rules than restaurants. Camp staff, administrators, counselors, food managers, and infirmary staff, should fulfil important roles in their respective areas to prevent future outbreaks.     

Risk factors for sporadic Campylobacter jejuni infections in rural michigan: a prospective case-control study

OBJECTIVES: This case-control study investigated risk factors for campylobacteriosis in a rural population. Exposure to live farm animals was hypothesized to increase the risk for Campylobacter jejuni enteritis. METHODS: Incident cases from rural counties reported to the Michigan Department of Community Health and matched controls completed a self-administered postal questionnaire. RESULTS: Persons engaged in poultry husbandry had increased odds of campylobacteriosis (odds ratio = 6.884; 95% confidence interval (CI) = 1.438, 32.954). There was evidence for a dose-response relationship between the number of types of poultry contact and campylobacteriosis. CONCLUSIONS: We estimate that 18% (95% CI = 6%, 30%) of Campylobacter cases occurring in rural populations are attributable to poultry husbandry. Cases occurred in individuals who were not poultry farmers by occupation.     

Escherichia coli O157:H7 outbreak linked to salami, British Columbia, Canada, 1999

An outbreak of E. coli O157:H7 infections was identified in November 1999 with a fivefold increase in the occurrence of laboratory-confirmed cases of E. coli O157:H7 infection. A matched case-control study was conducted. Samples of food from cases and from retailers were analysed for the presence of E. coli O157:H7. A total of 143 cases were identified over a 12-week period with the same pulsed-field gel electrophoresis (PFGE) pattern. The case-control study found that Company A salami was significantly associated with illness (Mantel-Haenszel matched odds ratio 10.0%, 95% CI 1.4-434, P=0.01). Company A salami tested positive for E. coli O157:H7 and isolates had the same PFGE pattern as case isolates. An immediate voluntary national recall of Company A dry fermented meat products took place. Findings from the investigation of this outbreak suggest that the hold-and-test option may not be adequate to prevent shiga-toxigenic Escherichia coli (STEC) infection in salami consumers.     

Epidemiologic and laboratory investigation of an outbreak of Campylobacter enteritis associated with raw milk

An outbreak of gastroenteritis occurred in March-April 1981, in Wichita, Kansas, and involved more than 250 persons who drank raw milk from a single local dairy. Campylobacter jejuni was recovered from 60 of 116 (52%) persons in households that had one or more ill family members. A cohort study of families that belonged to a food cooperative that purchased raw milk from the implicated dairy showed a significant association between illness and having drunk raw milk. Thirty-nine of 55 (71%) persons who drank raw milk became ill compared with four of 36 (11%) persons who did not drink raw milk (p less than 0.01, t test, accounting for clustering). Peak (convalescent) antibody titers to C. jejuni, determined by indirect immunofluorescence, in 20 raw-milk drinkers showed a geometric mean of 1:27 in contrast to geometric mean titer of 1:6 in 10 well persons from the cohort who did not drink raw milk (p less than 0.002, t test). C. jejuni was recovered from 21 of 34 (66%) raw-milk drinkers, versus none of 26 people who did not drink raw milk (p less than 0.001, Fisher's exact test, one tailed). C. jejuni of the same serotype was isolated from the case-patients and from rectal swabs of cows in the dairy. These findings indicate that raw milk contaminated by Campylobacter was the vehicle for this outbreak.     

Epidemiology of a large restaurant-associated outbreak of Shiga toxin-producing Escherichia coli O111:NM

In August 2008, a large outbreak of Shiga toxin-producing Escherichia coli (STEC) O111:NM infections associated with a buffet-style restaurant in rural Oklahoma was identified. A case-control study of restaurant patrons and a retrospective cohort study of catered event attendees were conducted coupled with an environmental investigation to determine the outbreak's source and mode of transmission. Of 1823 persons interviewed, 341 (18·7%) met the outbreak case definition; 70 (20·5%) were hospitalized, 25 (7·3%) developed haemolytic uraemic syndrome, and one died. Multiple food items were significantly associated with illness by both bivariate and multivariate analyses, but none stood out as a predominant transmission vehicle. All water, food, and restaurant surface swabs, and stool cultures from nine ill employees were negative for the presence of Shiga toxin and E. coli O111:NM although epidemiological evidence suggested the outbreak resulted from cross-contamination of restaurant food from food preparation equipment or surfaces, or from an unidentified infected food handler.     

An outbreak of Escherichia coli O157:H7 infections and haemolytic uraemic syndrome associated with consumption of unpasteurized apple cider

During October 1996, an outbreak of Escherichia coli O157:H7 infections among Connecticut residents occurred. An epidemiologic investigation included enhanced surveillance and a case-control study. Clinical isolates of Escherichia coli O157:H7 were typed by pulsed-field gel electrophoresis (PFGE). Implicated cider samples were analysed by culture and polymerase chain reaction (PCR). Consumption of implicated cider was associated with illness; (matched odds ratio = undefined, 95 % confidence interval = 3.5-infinity). Ultimately, a total of 14 outbreak-associated patients were identified. All isolates analysed by PFGE yielded the outbreak-associated subtype. Escherichia coli O157:H7 was not cultured from three cider samples; PCR analysis detected DNA fragments consistent with Escherichia coli O157:H7 in one. This outbreak was associated with drinking one brand of unpasteurized apple cider. PFGE subtyping supported the epidemiologic association. PCR analysis detected microbial contaminants in the absence of live organisms. Washing and brushing apples did not prevent cider contamination.     

A prolonged outbreak of Norwalk-like calicivirus (NLV) gastroenteritis in a rehabilitation centre due to environmental contamination

An outbreak of Norwalk-like calicivirus (NLV) gastroenteritis occurred in a rehabilitation centre in southern Finland between December 1999 and February 2000. An epidemiological investigation was conducted to determine the source and extent of the outbreak. More than 300 guests and staff members became ill during the outbreak. No food or activity in the centre could be linked epidemiologically to illness. NLV genogroup II was detected by RT-PCR in stool samples of symptomatic guests and employees. All strains reacted similarly with the microplate hybridization probe panel and showed the same nucleotide sequence, indicating that they represented the same NLV strain. Food and water samples were negative for NLV, whereas NLV was detected in three environmental specimens. The strains from patients and environment were identical based on microplate hybridization probes, suggesting that environmental contamination may have been important for the spread of calicivirus and the protracted course of the outbreak.     

An outbreak of waterborne giardiasis associated with heavy water runoff due to warm weather and volcanic ashfall

From mid-June through early August 1980, an outbreak of gastrointestinal illness in Red Lodge, Montana affected approximately 780 persons, as estimated from attack rates of 33 per cent and 15 per cent in urban and rural residents, respectively. Giardia lamblia was identified in stool specimens from 51 per cent of 47 persons with a history of untreated gastrointestinal illness and in 13 per cent of 24 specimens from asymptomatic persons (p = .00045, Fisher's Exact Test). The epidemic curve was bimodal with peaks in mid-June and mid-July. Each peak occurred about three weeks after an episode of very heavy water runoff resulting from warm sunny weather and snow darkened by ashfall from the Mt. St. Helens volcanic eruption of May 18, 1980. Unfiltered and inadequately chlorinated surface water was supplied by the city water system, which was implicated as the vehicle of transmission in the outbreak. Water systems providing unfiltered surface water are more likely to become contaminated during periods of heavy water runoff.     

An outbreak of Campylobacter jejuni gastroenteritis linked to meltwater contamination of a municipal well

A large outbreak of Campylobacter jujuni gastroenteritis attributed to contamination of an unchlorinated municipal water system was investigated. Unlike most previous summer outbreaks, this one began in early spring and was attributed to meltwater entering one or more municipal wells. 241 suspected cases were documented, but retrospective information from local health care workers suggested a much larger outbreak. 45 laboratory-confirmed cases participated in a case-control study which showed a significant association between infection and amount of town water consumed. Stool specimens from 29 patients were studied with detailed serotyping by the method of Lior, with eight known serotypes and one previously unknown one identified. It is concluded that intensive surveillance of water quality during periods of spring runoff is essential, and that timely reporting of disease outbreak patterns in emergency department settings is necessary to protect the public's health.     

Emerging genotype (GGIIb) of norovirus in drinking water, Sweden

From May through June 2001, an outbreak of acute gastroenteritis that affected at least 200 persons occurred in a combined activity camp and conference center in Stockholm County. The source of illness was contaminated drinking water obtained from private wells. The outbreak appears to have started with sewage pipeline problems near the kitchen, which caused overflow of the sewage system and contaminated the environment. While no pathogenic bacteria were found in water or stools specimens, norovirus was detected in 8 of 11 stool specimens and 2 of 3 water samples by polymerase chain reaction. Nucleotide sequencing of amplicons from two patients and two water samples identified an emerging genotype designated GGIIb, which was circulating throughout several European countries during 2000 and 2001. This investigation documents the first waterborne outbreak of viral gastroenteritis in Sweden, where nucleotide sequencing showed a direct link between contaminated water and illness.     

A case-cohort study to investigate concomitant waterborne outbreaks of Campylobacter and gastroenteritis in Söderhamn, Sweden, 2002-3

Increased domestic, laboratory confirmed, Campylobacter notifications were reported in Siderhamn municipality, December 2002 and January 2003. Concurrently, during preliminary investigations a large outbreak of acute gastroenteritis was detected. Simultaneously, two studies were completed to identify risk factors for infection with Campylobacter and acute gastrointestinal infection (AGI): (1) a case-cohort study using Campylobacter cases (N = 101) with a large random sample from the municipal population as referents (N = 1000) and (2) a retrospective cohort study for the outcome AGI using the same sample. A postal questionnaire was used to collect demographic, clinical, water and food consumption data. Measures of association (risk ratio (RR), odds ratio (OR)) and 95% confidence intervals (CI) were calculated. Stool, environmental and water samples were tested by standard methods at G?vle Hospital and SMI laboratories respectively. In the case-cohort study, Camplylobacter cases were more likely than referents to consume communal water (OR = 12.6 (95% CI 1.7-92.3)). In the cohort study, risk of gastroenteritis was 2.3 times higher in those who consumed water (AR = 27.3%) than others (AR = 12%). Risk of illness was associated with the amount of water consumed in both studies. Campylobacter was detected in stools and Escherichia coli (E. coli) from routine communal water (CW) samples. Results suggest both S?derhamn outbreaks of Campylobacter and AGI were associated with consumption of CW. The method used strengthened epidemiological evidence and was efficient in the use of time and resources.     

Cryptosporidiosis in Wisconsin: a case-control study of post-outbreak transmission.

During March-April 1993, an estimated 403000 residents of the 5-county greater Milwaukee, Wisconsin area developed cryptosporidiosis after drinking contaminated municipal water. Although the number of cases dropped precipitously after the implicated water plant closed on 9 April, cases continued to occur. To investigate risk factors for post-outbreak cryptosporidiosis, 33 Milwaukee-area residents who had laboratory-confirmed Cryptosporidium infection with onset of diarrhoea between 1 May and 27 June 1993 were interviewed by telephone. Of these, 28 (85%) had onset of diarrhoea during May, 12 (36%) had watery diarrhoea during the outbreak, and 5(15%) were HIV-infected. In a neighbourhood-matched case-control study, immunosuppression (matched odds ratio (MOR) not calculable, 95% confidence interval (CI) 3.0, infinity) and having a child less than 5 years old in the household (MOR = 17.0, CI 2.0, 395.0) were independently associated with infection. When persons who had diarrhoea during the outbreak were excluded, immunosuppression remained significantly associated with illness (MOR not calculable, CI 1.6, infinity). Cryptosporidium transmission continued after this massive waterborne outbreak but decreased rapidly within 2 months.     

Norwalk Gastroenteritis Associated with a Water System in a Rural Georgia Community

An outbreak of acute gastroenteritis occurred during January 4–9, 1982, in a rural community in north Georgia. A systematic telephone survey revealed that 63% of persons living in homes served by the community water system had symptoms of acute gastroenteritis in contrast to 9% of persons in homes served by private wells or other sources (P < .001). A fourfold rise in antibody titer to the Norwalk virus occurred in 20 of 22 serum pairs obtained from ill persons. Fecal coliforms (> 16 MPN/100 ml) were detected in a spring which served as one water source for the community system. Surface runoff from a heavy rainfall, which preceded the outbreak, may have contaminated the system. Outbreaks of gastroenteritis should be promptly reported and investigated to facilitate corrective measures and to identify causative agents such as Norwalk virus.