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PubMed1990

DNA restriction digest and ribosomal RNA gene patterns of Campylobacter jejuni: a comparison with bio-, sero-, and bacteriophage-types of United Kingdom outbreak strains.

DNA restriction endonuclease (Hae III and Hind III) total digest and 16S and 23S ribosomal (r)RNA gene patterns (ribopatterns) were determined for 18 isolates of Campylobacter jejuni from three separate outbreaks of diarrhoea in the north of England. Strains were also characterized by biotyping, serotyping and phage typing. Comparisons of the DNA patterns by visual and numerical methods revealed five distinct strain groupings with clear differences between isolates from different outbreaks as well as some heterogeneity between strains within the community outbreak and one of the school outbreaks. An excellent correlation was observed between the genomic DNA fingerprints data and the Preston bacteriophage group, both of which gave better discrimination than biotyping and serotyping alone or in combination. Only one phage group (PG 37) was not confirmed by the DNA data. DNA fingerprints therefore provide additional information of value in studying the epidemiology of outbreaks of C. jejuni.

Animals↗

PubMed1996

Consecutive salmonella outbreaks traced to the same bakery.

Two consecutive community outbreaks of Salmonella enteritidis phage type 4 (PT4) traced to the same bakery occurred in Cardiff, Wales during August-September 1992. In the first outbreak, illness was associated with eating custard slices (odds ratio 23.8, 95% confidence interval 6.5-94.4, P < 0.0001), and in the second, with eating fresh cream cakes (odds ratio 15.8, 95% confidence interval 1.6-374, P = 0.004). Environmental investigations implicated cross-contamination during preparation of the cold-custard mix as the cause of the first outbreak, and inadequate cleaning and disinfection of nozzles used for piping cream in the second outbreak. S. enteritidis PT4 was isolated from fresh cream sponge cake retained by a case and from two fresh cream cakes and four environmental swabs obtained at the bakery. This incident illustrates the hazard of widespread environmental contamination with salmonella and the need for thorough environmental cleansing for any premises implicated in an outbreak of food poisoning.

Adolescent↗

PubMed1996

Virulence and genotype stability of Salmonella enterica serovar Berta during a natural outbreak.

Strains of Salmonella enterica serotype Berta, collected over a period of 6 years from a well documented natural outbreak in Denmark, have been characterized in order to assess the stability of chromosomal typing systems and virulence properties. Outbreak strains were identical in Pvu II and PSTI IS200 profiles, all but two strains showed the same Sma I ribotype, and all but one strain showed the same Not I pulsed field gel electrophoretic pattern, indicating that these molecular markers remained almost constant during the outbreak. In general, strains of S. Berta were found to be of moderate to low virulence; log VC10 values were found to vary between 3.0 and 4.4 after i.p. challenge of mice, and maximum CFU in internal organs of day-old chicks varied between 2 and 4 log10 units following oral challenge. The minor differences observed between strains in vivo did not correlate with differences in in vitro invasion into cultured MDCK cells, nor with in vitro growth characteristics. A succession of different plasmid profile types was observed during the outbreak but a hierarchical selection of clones based on differences in virulence was unlikely to have caused the succession of types of S. Berta during this outbreak.

Animals↗

PubMed1991

Variation in time and space of non-outbreak Legionnaires' disease in Scotland.

The main aim of this study was to measure and explain geographic variations in the incidence of Legionnaires' disease in Scotland, particularly to help understand the source of non-outbreak infection. Between 1978 and 1986 the overall mean annual incidence rate was 7.9 per million (range 3.1-20.2), and for non-outbreak, non-travel cases it was 5.6. There were geographical variations by health board, by city and within cities, e.g. the mean annual incidence rate per million for non-travel, non-outbreak disease was 1.2 in Tayside Health Board, 3.7 in Lanarkshire, 5.6 in Lothian and 14.4 in Greater Glasgow. In Greater Glasgow Health Board non-travel cases lived in and around the city centre and in some postcode sectors there, the mean annual incidence rate exceeded 100. Travel-related cases lived in peripheral areas. These variations could not be explained by differences in access to and use of diagnostic services, surveillance, or host susceptibility (as reflected by socioeconomic status and frequency of other respiratory disease). The explanation probably lay in environmental factors, though differences in agent virulence were not excluded. The two main conclusions are, that non-outbreak cases were not truly sporadic, and that the space-time variations in incidence support the hypothesis that cooling towers were an important source of infection for non-travel, non-outbreak cases. If so such infection is potentially preventable.

Adolescent↗

PubMed1993

A model for autumn outbreaks of Legionnaires' disease associated with cooling towers, linked to system operation and size.

Cooling towers have been demonstrated to be amplifiers and disseminators of legionella, the causative organism of Legionnaires' disease. Community outbreaks associated with cooling towers have been reported with several common factors. Small towers (< 300 kW) have predominantly been implicated in outbreaks. Cooling tower-associated outbreaks are most frequent in autumn, and frequently implicated systems have been operated after a period of shutdown. This paper reports field study data relating system operation to legionella colonization of systems. Operating systems have been shown to be more frequently colonized by legionella than shutdown systems. In some cases operation of systems after periods of shutdown raised legionella concentrations from below detection limits to between 50 and 950 c.f.u./ml within 10 min. These data and previously reported data relating to biofilm and sediment colonization of the systems, and community outbreaks of Legionnaires' disease, have been used to develop a model explaining the seasonal nature of outbreaks associated with irregularly operated, small cooling tower systems.

Air Conditioning↗

PubMed1996

An outbreak of cholera from food served on an international aircraft.

In February 1992, an outbreak of cholera occurred among persons who had flown on a commercial airline flight from South America to Los Angeles. This study was conducted to determine the magnitude and the cause of the outbreak. Passengers were interviewed and laboratory specimens were collected to determine the magnitude of the outbreak. A case-control study was performed to determine the vehicle of infection. Seventy-five of the 336 passengers in the United States had cholera; 10 were hospitalized and one died. Cold seafood salad, served between Lima, Peru and Los Angeles, California was the vehicle of infection (odds ratio, 11.6; 95% confidence interval, 3.3-44.5). This was the largest airline-associated outbreak of cholera ever reported and demonstrates the potential for airline-associated spread of cholera from epidemic areas to other parts of the world. Physicians should obtain a travel history and consider cholera in patients with diarrhoea who have travelled from cholera-affected countries. This outbreak also highlights the risks associated with eating cold foods prepared in cholera-affected countries.

Adolescent↗

PubMed2001

Epidemiological investigation of the central Scotland outbreak of Escherichia coli O157 infection, November to December 1996.

On Friday, 22 November 1996, the microbiologist at a hospital in Lanarkshire, Scotland, identified presumptive Escherichia coli O157 in faecal specimens submitted by three patients with bloody diarrhoea, and confirmed its presence in one. Over the next 6 h, 12 more potential cases were identified. Investigations first indicated then confirmed a single food premises as the source of infection. Effective control measures were applied promptly. The outbreak was declared over on 20 January 1997, by which time 512 cases had been identified, and infection with the outbreak strain confirmed in 279. Twenty deaths occurred in cases during the outbreak and there were two more in cases during 1997. Seventeen of these deaths resulted from the outbreak. This paper describes the outbreak's epidemiological investigation, referring to other investigations, and control measures, where appropriate.

Adolescent↗

PubMed2002

Prevalence of Salmonella typhimurium infection in Norwegian hedgehog populations associated with two human disease outbreaks.

Faecal carriage of salmonella was investigated in 320 hedgehogs from Moss municipality in south-eastern Norway, Askøy, Bergen and Os municipalities in central-western Norway, and five municipalities in south-western and central Norway. The sampling in Moss was carried out 1 year after a human outbreak of salmonellosis, whereas the sampling in Askøy, Bergen and Os was carried out during a human outbreak. Both outbreaks were caused by Salmonella Typhimurium 4,5,12:i:1,2. No salmonella were detected in the hedgehogs from south-western (0/115) and central (0/24) Norway. Thirty-nine percent (39/99) of the animals sampled on Jeløy, and 41% (34/82) of those from Askøy, Bergen and Os, carried S. Typhimurium 4,5,12:i:1,2. The PFGE profile of isolates from hedgehogs and human beings were identical within each of the two outbreak areas. A significantly higher carrier rate of S. Typhimurium occurred among hedgehogs sampled at feeding places, compared to those caught elsewhere. The salmonella-infected hedgehog populations most likely constituted the primary source of infection during both of the human disease outbreaks, and the Norwegian hedgehog is suggested as a reservoir host of S. Typhimurium 4,5,12:i:1,2.

Animals↗

PubMed2002

E. coli O157 phage type 21/28 outbreak in North Cumbria associated with pasteurized milk.

In March 1999, a large community outbreak of Escherichia coli O157 infection occurred in North Cumbria. A total of 114 individuals were reported to the Outbreak Control Team (OCT); 88 had laboratory confirmed E. coli O157. Twenty-eight (32%) of the confirmed cases were admitted to hospital, including three children (3.4%) with haemolytic uraemic syndrome. There were no deaths. A case-control study found that illness was strongly associated with drinking pasteurized milk from a local farm (P = <0.0001) on single variable analysis. Microbiological investigations at the farm revealed E. coli O157 phage type (PT) 21/28 VT 2 which was indistinguishable from the human isolates by pulsed field gel electrophoresis. At the time of occurrence this was the largest E. coli O157 outbreak in England and Wales and the first E. coli O157 PT 21/28 VT 2 outbreak associated with pasteurized milk. This outbreak highlights lessons to be learnt regarding on-farm pasteurization.

Adolescent↗

PubMed2004

Waterborne outbreak of gastroenteritis in a religious summer camp in Norway, 2002.

In July 2002 an outbreak of acute gastroenteritis occurred in a camp facility in western Norway during a 10-day seminar, with around 300 guests staying overnight and several day-time visitors. Environmental and epidemiological investigations were conducted to identify and eliminate the source of the outbreak, prevent further transmission and describe the impact of the outbreak. Of 205 respondents, 134 reported illness (attack rate, 65%). Multivariate analysis showed drinking water and taking showers at the camp-site to be significant risk factors. Secondary person-to-person spread among visitors or outside of the camp was found. Norovirus was identified in 8 out of the 10 stool samples analysed. Indicators of faecal contamination were found in samples from the private untreated water supply, but norovirus could not be identified. This outbreak investigation illustrates the importance of norovirus as a cause of waterborne illness and the additional exacerbation through person-to-person transmission in closed settings. Since aerosol transmission through showering contributed to the spread, intensified hygienic procedures such as isolation of cases and boiling of water may not be sufficient to terminate outbreaks with norovirus.

Camping↗

PubMed2004

A syphilis outbreak in remote Australia: epidemiology and strategies for control.

This paper describes the epidemiology of a syphilis outbreak in remote Australia, and explores contributing factors and control strategies. Between 1 August 2000 and 31 January 2002, 74 cases of early syphilis (42 female, 32 male) were identified in 73 Kimberley residents. Syphilis rates in age groups 10-19 and 20-29 years were 583 and 439 per 100000 person years respectively. Factors contributing to the outbreak included incompleteness of sexually transmitted infection (STI) clinical management, untimely contact tracing, staffing and management issues, and poor community knowledge about STIs. Outbreak control strategies addressed factors that could be influenced by changes in health service delivery, and focused on providing education and support to health staff, and efforts to increase community knowledge about sexual health. Although some improvements have occurred, the outbreak is still continuing. Until open and honest discussion and a collaborative approach is taken toward STI problems affecting Indigenous Australians, outbreaks such as this will continue to occur.

Adolescent↗

PubMed2005

Use of AFLP and PFGE to discriminate between Salmonella enterica serovar Typhimurium DT126 isolates from separate food-related outbreaks in Australia.

In 2001 Salmonella enterica serovar Typhimurium definitive phage-type (DT) 126 was isolated at higher frequency in Australia compared to other S. Typhimurium phage types and in comparison to previous years. Associated with this increase was the implication of this phage type in a number of food-related outbreaks. We compared fluorescent amplified fragment length polymorphism (FAFLP) to pulsed-field gel electrophoresis (PFGE), the current 'gold standard' for molecular typing of Salmonella for the discrimination between outbreak-associated isolates and epidemiologically unrelated DT126 strains. FAFLP showed a greater ability to discriminate between isolates than PFGE, with 16 groups of clusters or individual isolates with < 90% similarity to each other compared to three groups as determined by PFGE. Both methods were able to discriminate between isolates from two separate outbreaks in South Australia and isolates associated with an outbreak at a restaurant in New South Wales. The resolving power of both methods was not sufficient to separate all epidemiologically unrelated DT126 isolates from the outbreak isolates. We conclude that amplified fragment length polymorphism is a useful tool to assist in the discrimination of S. Typhimurium DT126 isolates.

Bacteriophage Typing↗

PubMed2006

Public health implications of a case of haemolytic-uraemic syndrome associated with a concomitant outbreak of mild gastroenteritis in a small rural community.

The concomitant occurrence of a case of haemolytic-uraemic syndrome (HUS) and 62 cases of mild gastroenteritis in schools of a small rural community in southern Italy induced the health authorities to suspect a foodborne outbreak of shiga-toxin-producing Escherichia coli (STEC) infection. The schools were closed and the catering service involved was investigated. However, STEC were not isolated from the HUS case or from the 56 cases of gastroenteritis examined, and the HUS case and the outbreak of gastroenteritis were probably just coincidental. A retrospective cohort study failed to show any correlation with consumption of school meals and suggested that the outbreak probably started outside the school setting and then spread within the schools by person-to-person transmission. All the cases examined were negative for common enteric pathogens and the responsible agent for the cases of gastroenteritis was not identified. The concern raised in the small community by the occurrence of a severe case of HUS and the lack of a rapid epidemiological assessment excluding the occurrence of a STEC outbreak, turned an epidemic episode of mild gastroenteritis into a public health emergency with relevant socioeconomic consequences. Prompt intervention in outbreaks following timely and effective risk communication are crucial for taking the most appropriate control measures and avoiding the spread of fear and panic in the community.

Child↗

PubMed2006

Comparing Shigella waterborne outbreaks in four different areas in Greece: common features and differences.

In Greece the public health surveillance for most infectious diseases, including shigellosis, is not well developed. However, four waterborne outbreaks of shigellosis have been recorded in Greece in the last three decades, in different areas of the country, under different environmental and socioeconomic conditions. This study presents the epidemiological characteristics of these four outbreaks in order to examine common points and differences and to investigate their possible association with environmental and socioeconomic conditions. All four outbreaks were caused by Shigella sonnei and related to drinking water. Epidemic curves, distribution of cases by age and gender, hospitalization rates, environmental conditions and laboratory results were compared. The outbreaks seemed to correspond to two different 'models' presenting two characteristic types of epidemic waves related to specific environmental conditions. The attack rates for the general population varied from about 9 to 13% and were similar for both sexes. Children were affected mostly. In these outbreaks there was a strong suspicion of contamination of the water distribution system from the sewage network, highlighting the importance of environmental health control measures.

Adolescent↗

PubMed2006

Recurrent outbreaks of cryptosporidiosis associated with calves among students at an educational farm programme, Minnesota, 2003.

Enteric illness outbreaks among middle-/high-school students in consecutive semesters of an educational farm programme were investigated with retrospective cohort studies. During the first outbreak, 31/92 (34%) interviewed students were ill. Risk factors included participating in animal science class (RR 8.1, 95% CI 1.2-55.2) and contact with calves (RR 4.2, 95% CI 1.1-16.2). Stool samples from seven students and two calves yielded Cryptosporidium parvum. Students cared for animals in street clothes and practised poor hand washing. During the second outbreak, 37/81 (46%) interviewed animal science students were ill. Risk factors included having visible manure on hands, and wearing coveralls and boots. Stool samples from seven students and eight calves yielded C. parvum. Student hand washing was still inadequate. Coveralls/boots were cleaned infrequently and removed after hand washing. These outbreaks of cryptosporidiosis resulted from calf contact and inadequate hygiene practices. The failure to adequately implement recommended interventions contributed to the second outbreak.

Adolescent↗

PubMed2006

The use of outbreak information in the interpretation of clustering of reported cases of Escherichia coli O157 in space and time in Alberta, Canada, 2000-2002.

We obtained a list of all reported cases of Escherichia coli O157 in Alberta during the 2000-2002 period, and using scan statistics we identified yearly temporal and spatial clusters of reported cases of E. coli O157 during the summer and in southern Alberta. However, the location of the spatial cluster in the south was variable among years. The impact of using both outbreak and sporadic data or only sporadic data on the identification of spatial and temporal clusters was small when analysing individual years, but the difference between spatial clusters was pronounced when scanning the entire study period. We also identified space-time clusters that incorporated known outbreaks, and clusters that were suggestive of undetected outbreaks that we attempted to validate with molecular data. Our results suggest that scan statistics, based on a space-time permutation model, may have a role in outbreak investigation and surveillance programmes by identifying previously undetected outbreaks.

Alberta↗

PubMed1997

The role of young children in a community-wide outbreak of hepatitis A.

An Hasidic Jewish community has experienced recurrent hepatitis A outbreaks since 1980. To assess risk factors for illness during a 1985-6 outbreak, the authors reviewed case records and randomly selected 93 households for an interview and serologic survey. In the outbreak, 117 cases of hepatitis A were identified, with the highest attack rate (4.2%) among 3-5 year olds. Among the survey households, the presence of 3-5 year olds was the only risk factor that increased a household's risk of hepatitis A (indeterminant relative risk, P = 0.02). Furthermore, case households from the outbreak were more likely to have 3-5 years olds than were control households from the survey (odds ratio = 16.4, P < 0.001). Children 3-5 years old were more likely to have hepatitis A and may have been the most frequent transmitters of hepatitis A in this community. Hepatitis A vaccination of 3-5 year olds can protect this age group and might prevent future outbreaks in the community.

Adolescent↗

PubMed1998

Surveillance data for waterborne illness detection: an assessment following a massive waterborne outbreak of Cryptosporidium infection.

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 nonconfounded 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.

Bias↗