An outbreak of food-borne botulism in Scotland, United Kingdom, November 2011

An investigation is currently underway to explain an outbreak of food-borne botulism in Scotland. Three children in the same family were confirmed as having botulism following consumption of a meal made with a jar of korma sauce. Residual sauce from the jar, the jar lid and a remnant of the meal, all tested positive for Clostridium botulinum type A toxin. The children are recovering, although two remain ventilated and in intensive care unit.

Temperature-dependent transmission of rotavirus in Great Britain and The Netherlands

In Europe, rotavirus gastroenteritis peaks in late winter or early spring suggesting a role for weather factors in transmission of the virus. In this study, multivariate regression models adapted for time-series data were used to investigate effects of temperature, humidity and rainfall on reported rotavirus infections and the infection-rate parameter, a derived measure of infection transmission that takes into account population immunity, in England, Wales, Scotland and The Netherlands. Delayed effects of weather were investigated by introducing lagged weather terms into the model. Meta-regression was used to pool together country-specific estimates. There was a 13 per cent (95% confidence interval (CI), 11-15%) decrease in reported infections per 1 degrees C increase in temperature above a threshold of 5 degrees C and a 4 per cent (95% CI, 3-5%) decrease in the infection-rate parameter per 1 degrees C increase in temperature across the whole temperature range. The effect of temperature was immediate for the infection-rate parameter but delayed by up to four weeks for reported infections. There was no overall effect of humidity or rainfall. There is a direct and simple relationship between cold weather and rotavirus transmission in Great Britain and The Netherlands. The more complex and delayed temperature effect on disease incidence is likely to be mediated through the effects of weather on transmission.

Clinical management of children with suspected or confirmed E. coli O157 infection

Scotland continues to report higher rates of infection with Escherichia coli O157 than elsewhere in the UK. Infection with E. coli O157 usually manifests as acute, afebrile, painful, bloody diarrhoea and is the commonest cause of Haemolytic Uraemic Syndrome (HUS), an important cause of childhood renal failure. In 1996 an outbreak of E. coli O157 infection in Central Scotland, resulted in over 500 cases and 17 deaths. Ten years on, high-profile outbreaks of E. coli O157 infection in Scotland still result in cases of HUS and fatalities. We sought to identify outcomes and describe pre-hospital clinical management strategies using prospective, national surveillance of paediatric HUS cases, from 2003 to 2006 inclusive. We recommend that children who present with acute, afebrile, and painful bloody diarrhoea be referred to hospital as early as possible for appropriate clinical management.

How protective is breast feeding against diarrhoeal disease in infants in 1990s England? A case-control study

AIMS

To assess the effect of several measures of infant feeding on diarrhoeal disease, and whether these effects vary according to markers of social deprivation.

METHODS

Case-control study of diarrhoeal disease cases presenting to 34 general practices in England. Controls were stratified on age group, area deprivation index for the practice, and whether or not the practice was in London. Data were available on 304 infants (167 cases and 137 controls).

RESULTS

After adjustment for confounders, breast feeding was associated with significantly less diarrhoeal disease. Associations were striking even in infants aged > or = 6 months. They did not vary by social class, but were greater in those living in rented council accommodation and in more crowded households. The effect of receiving no breast milk was stronger in more deprived areas than in less deprived areas. The effect of not receiving exclusive breast milk was stronger in more deprived areas than in less deprived areas. In formula fed infants, there was significantly more diarrhoeal disease in those not sterilising bottles/teats with steam or chemicals. The protective effect of breast feeding did not persist beyond two months after breast feeding had stopped.

CONCLUSIONS

Breast feeding protects against diarrhoeal disease in infants in England although the degree of protection may vary across infants and wear off after breast feeding cessation. Education about the benefits of breast feeding and the risks of inadequate sterilisation should be targeted at carers in deprived areas or households.

Epidemiology of Salmonella enterica serovars Enteritidis and Typhimurium in animals and people in Scotland between 1990 and 2001

Two serovars of salmonella which are currently of particular importance in both human and animal infections are Salmonella enterica serovars Enteritidis phage type 4 (PT4) and Typhimurium definitive type 104 (DT104). This paper describes the trends in the relationships between the levels of infection of people and a range of farm animal species with these two serovars and explores some of the reasons behind them. In 1996, there was a peak of 520 reports of S Typhimurium DT104 infection in people in Scotland, but the number has decreased every year since, to 96 in 2001. In cattle the incidence of S Typhimurium DT104 also peaked in 1996, with 138 incidents, and it has similarly decreased every year to 2001 when there were 10 reported incidents. Similar declines have been observed in its incidence in sheep and pigs. In people the number of reports of S Enteritidis PT4 peaked in 1997 at 1684 and then declined to 457 in 2001. In chickens, the number of reports of S Enteritidis PT4 peaked in 1998 at 34 incidents, but no incidents were reported in the following three years.

A European outbreak of Salmonella enterica serotype Typhimurium definitive phage type 204b in 2000

OBJECTIVE

To describe the clinical, epidemiologic and microbiological features of a large outbreak of infection with a multiresistant Salmonella enterica serotype Typhimurium definitive type DT204b infection involving at least 392 people in five European countries.

METHODS

Icelandic public-health doctors responded to a report on an Internet news site of an outbreak of infection with a multiresistant strain of Typhimurium DT104 in England by contacting the Public Health Laboratory Service (PHLS) Communicable Disease Surveillance Centre (CDSC). An international alert was sent out through Enter-net. All strains from England & Wales, The Netherlands, Scotland and Germany, and 17 of the outbreak isolates from Iceland, were phage-typed, screened for antimicrobial resistance, and subjected to molecular typing. Hypothesis-generating interviews were conducted, followed by case-control studies performed in Iceland and England.

RESULTS

Isolates from cases in Iceland, England and Wales, The Netherlands, Scotland and Germany were identified as Typhimurium DT204b. The antimicrobial resistance pattern was ACGNeKSSuTTmNxCpL. All strains tested displayed an identical plasmid profile. Strains from five cases in England & Wales and five cases in Iceland possessed identical pulsed-field profiles. Although a common source was suspected, only Iceland implicated imported lettuce as a vehicle, with an analytic epidemiologic study (OR = 40.8; P = 0.005; 95% CI 2.7-3175).

CONCLUSION

The identification of international outbreaks, necessary for investigation and control, can be facilitated by standardized phage-typing techniques, the electronic transfer of molecular typing patterns, formal and informal links established through international surveillance networks, and the early reporting of national outbreaks to such networks.

The infectious intestinal disease study of England: a prospective evaluation of symptoms and health care use after an acute episode

The sequelae of Infectious Intestinal Disease (IID) in a population-based sample of cases and matched controls were investigated for a period of 3 months following the initial infection. Incident cases of IID presenting to GPs or occurring in the community and controls were studied at 3 weeks and over a 3-month follow-up period. Cases were six times more likely than controls to have gastrointestinal symptoms, particularly diarrhoea, at 3 weeks. Ten per cent of cases consulted their GP in the 3 months after episode and 2.3% were referred to hospital. GP presentation rates were twice as high in cases. Gastrointestinal symptoms persist after IID, leading to an increased likelihood of GP consultation and hospital referral. Diagnosis of irritable bowel syndrome may be more likely following IID. The burden of IID is likely to be considerable given its high incidence and the frequency of such sequelae.

Surveillance of foodborne outbreaks of infectious intestinal disease in England and Wales 1992-1999: contributing to evidence-based food policy?

Between 1992 and 1999, a total of 1426 general outbreaks of infectious intestinal disease reported to the Public Health Laboratory Service (PHLS) Communicable Disease Surveillance Centre (CDSC) were described as foodborne. Where the evidence base to support the conclusions drawn was provided (66.3% of outbreaks) a combination of microbiological and analytical evidence was reported in 4% of outbreaks (60/1426); microbiological evidence alone in 10% of outbreaks (149/1426); analytical evidence alone in 23% of outbreaks (322/1426); microbiological evidence in combination with descriptive epidemiology in 3% of outbreaks (46/1426) and descriptive epidemiology alone in 26% of outbreaks (365/1426). Information supplied to CDSC by local investigators appears to be of varying quality and depth and may be influenced by the individual characteristics of outbreaks such as size and duration, outbreak setting, causative organism, vehicles of infection and time of year. These findings have implications for the use of these surveillance data in developing evidence-based food policy.

Foodborne infectious risks: do we need a wide system of data collection and survey? The lessons learned from the study of infectious intestinal disease in England

In 2000, the United Kingdom Government's Food Standards Agency published "A report of the study of infectious intestinal disease in England". This report was the result of over a decade's endeavour and cost well in excess of 2 million pound sterling (approximately 3.3 million euros). The study originated in 1989. In response to national epidemics of foodborne infection with Salmonella enteritidis phage type 4 and Listeria monocytogenes, the Government set up the Committee on the Microbiological Safety of Food (the Richmond Committee). This committee wished to know the actual level of clinical disease in the population giving rise to the laboratory reports of gastro-intestinal pathogens in national surveillance data and recommended studies to achieve this objective. In addition, successors to the to Richmond Committee decided that it would be of value to collect information from both cases and controls, including documenting exposure to biologically plausible risk factors so that differences between the ill and the well could be identified. Enquiries were also made about the clinical course of disease, so that long term sequelae and socio-economic costs could be estimated. A full description of this enormous study is beyond the scope of this paper, which defends the personal view that resources might have been better spent on a less ambitious enquiry.

The study of infectious intestinal disease in England: risk factors for cases of infectious intestinal disease with Campylobacter jejuni infection

This is a case-control study aimed at identifying risk factors for intestinal infection with Campylobacter jejuni. Cases were defined as subjects with diarrhoea occurring in community cohorts or presenting to General Practitioners (GPs) with Campylobacter jejuni in stools. Controls were selected from GP lists or cohorts, matched by age, sex, and GP practice. Travel abroad and consumption of chicken in a restaurant were statistically significantly associated with being a case. There was no statistically significant risk associated with consumption of chicken other than in restaurants nor with reported domestic kitchen hygiene practices. Consumption of some foods was associated with a lower risk of being a case. Most cases remained unexplained. We suggest that infection with low numbers of micro-organisms, and individual susceptibility may play a greater role in the causation of campylobacter infection than previously thought. It is possible that in mild, sporadic cases infection may result from cross contamination from kitchen hygiene practices usually regarded as acceptable. Chicken may be a less important vehicle of infection for sporadic cases than for outbreaks, although its role as a source of infection in both settings requires further clarification in particular in relation to the effect of domestic hygiene practices. The potential effect of diet in reducing the risk of campylobacteriosis requires exploration.

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.

A study of infectious intestinal disease in England: risk factors associated with group A rotavirus in children

OBJECTIVE

To identify risk factors for infectious intestinal disease (IID) due to rotavirus group A in children aged under 16 years.

METHODS

Case-control study of cases of IID with rotavirus infection presenting to general practitioners (GPs) or occurring in community cohorts, and matched controls.

RESULTS

There were 139 matched pairs. In children under 16 years the following risk factors were significantly associated with rotavirus IID: living in rented council housing (adjusted OR = 3.78, P = 0.022), accommodation with more than five rooms (OR = 0.72, P = 0.002), contact with someone ill with IID (OR = 3.45, P < 0.001). Some foods were associated with decreased risk. In infants, bottle feeding with or without breast feeding was associated with increased risk (OR = 9.06, P < 0.05).

CONCLUSIONS

Contact with persons with IID, living in rented council housing and accommodation with fewer rooms, were significant risk factors for sporadic rotavirus IID in children whereas breast feeding is protective in infants.

Investigation and management of sporadic gastrointestinal infections with potentially Vero cytotoxin producing Escherichia coli in Scotland

Recognition of the potential of Escherichia coli O157 and other Vero cytotoxin producing E. coli (VTEC) organisms to cause serious disease led to the recommendation that all diarrhoeal stool specimens be examined for E. coli O157. National guidelines exist for the testing and exclusion of cases and contacts of VTEC infection. A survey was conducted to discover the extent to which these recommendations are followed in Scotland by asking about current practices for public health management of identified cases and laboratory investigation of E. coli infection. About two thirds of Scottish health boards followed national guidelines for testing and exclusion of cases and contacts of VTEC O157 infection. Most laboratories tested all diarrhoeal stools for E. coli O157 but detection methods varied and a minority tested selected stools for non-O157 E. coli serogroups. Standardisation of policies for laboratory testing of VTEC infection would improve national surveillance. Adherence to evidence based guidelines would standardise public health management of VTEC infections in Scotland.

Food poisoning notification: time for a rethink

The notification of food poisoning is a statutory obligation of medical practitioners in the United Kingdom. Its objectives and methods are vague and ill documented, and the value of its output doubtful. Statutory notification of food poisoning is poor at identifying outbreaks, or single cases of severe disease, or as a measure of longer term trends. It should be fundamentally reformed.

A study of infectious intestinal disease in England: plan and methods of data collection

The Committee on the Microbiological Safety of Food, set up in 1989 by the Department of Health in response to national epidemics of foodborne infection, considered the available evidence and commissioned a study of infectious intestinal disease (IID) in England. Seventy practices (with 489,500) patients overall) recruited from the Medical Research Council's General Practice Research Framework between August 1993 and January 1995 collected data for one year. The practice populations were representative of practices in England by area and urban/rural location, but with fewer small and affluent practices. There were five main components. i) A population cohort of 9776 (40% of those eligible) were enrolled to estimate the incidence and aetiology of IID in the community, and a large proportion were followed up. A median of 10% of patients on practice age-sex registers had moved away or died. ii) A nested case control component based on cases ascertained in the cohort was used to identify risk factors for IID in the community. iii) In a case control component used to identify risk factors and to estimate the incidence and aetiology of IID presenting in 34 general practices 70% of the 4026 cases returned risk factor questionnaires, 75% submitted stools, and matched controls were found for 75% of cases. iv) An enumeration component was used to estimate the incidence of IID presenting to general practitioners (GPs) in 36 practices and the proportion of specimens sent routinely for microbiological examination. v) In a socioeconomic costs component used to estimate the burden of illness of IID in the community and presenting to GPs 63% of those who returned a risk factor questionnaire also returned a socioeconomic questionnaire and were representative by age, sex, and social class. Despite variable enrolment and compliance the study sample had sufficient power for the multivariable analysis. The characteristics associated with low enrollment and compliance must be considered in the interpretation of the main study results.

Study of infectious intestinal disease in England: rates in the community, presenting to general practice, and reported to national surveillance. The Infectious Intestinal Disease Study Executive

OBJECTIVE

To establish the incidence and aetiology of infectious intestinal disease in the community and presenting to general practitioners. Comparison with incidence and aetiology of cases reaching national laboratory based surveillance.

DESIGN

Population based community cohort incidence study, general practice based incidence studies, and case linkage to national laboratory surveillance.

SETTING

70 general practices throughout England.

PARTICIPANTS

459 975 patients served by the practices. Community surveillance of 9776 randomly selected patients.

MAIN OUTCOME MEASURES

Incidence of infectious intestinal disease in community and reported to general practice.

RESULTS

781 cases were identified in the community cohort, giving an incidence of 19.4/100 person years (95% confidence interval 18.1 to 20.8). 8770 cases presented to general practice (3.3/100 person years (2.94 to 3.75)). One case was reported to national surveillance for every 1.4 laboratory identifications, 6.2 stools sent for laboratory investigation, 23 cases presenting to general practice, and 136 community cases. The ratio of cases in the community to cases reaching national surveillance was lower for bacterial pathogens (salmonella 3.2:1, campylobacter 7.6:1) than for viruses (rotavirus 35:1, small round structured viruses 1562:1). There were many cases for which no organism was identified.

CONCLUSIONS

Infectious intestinal disease occurs in 1 in 5 people each year, of whom 1 in 6 presents to a general practitioner. The proportion of cases not recorded by national laboratory surveillance is large and varies widely by microorganism. Ways of supplementing the national laboratory surveillance system for infectious intestinal diseases should be considered.

Outbreaks of infectious intestinal disease in residential institutions in England and Wales 1992-1994

Data from the surveillance scheme of all general outbreaks of infectious intestinal disease in England and Wales reported to or otherwise identified, by the Public Health Laboratory Service Communicable Disease Surveillance Centre (CDSC) in 1992 and 1994 were used to describe the epidemiology of outbreaks of infectious intestinal disease in residential institutions. Outbreaks in residential institutions accounted for 22% (282/1275) of all outbreaks with most, 95% (268/282), occurring in homes for the elderly. The commonest pathogens in these 282 outbreaks were small round structured viruses 48% (132), salmonellas 17% (49). Clostridium perfringens 8% (23), rotavirus 5% (15) and Shigella sonnei 2% (6). The mode of transmission was described as mainly person to person in 71% (200 outbreaks) and mainly foodborne in 21% (58 outbreaks). The mean duration of outbreaks was 9 days. Duration of outbreaks varied with both the mode of transmission and the pathogen involved. The mean attack rate was 37%. Illness was reported in 5872 people. One or more individuals were admitted to hospital in 22% of outbreaks. Twenty-six deaths were reported, of which 18 were attributed to salmonellosis. Outbreaks in residential institutions are common. Attack rates are high and outbreaks are often prolonged, with high morbidity and mortality. There is a need for effective infection control policies which include appropriate training of staff, simple surveillance systems and readily available expert advice to ensure outbreaks are rapidly controlled.

General outbreaks of infectious intestinal disease in England and Wales 1992 to 1994

Data from the surveillance scheme of general outbreaks of infectious intestinal disease in England and Wales, reported to the PHLS Communicable Disease Surveillance Centre (CDSC), were used to review 1280 of the 1594 outbreaks identified between 1 January 1992 and 31 December 1994 for which a minimum data set was captured. The number of outbreaks reported in each regional health authority ranged from 31 in Mersey to 221 in Yorkshire. The commonest pathogens reported were salmonellas in 32% (412) of outbreaks, small round structured virus (SRSV) in 27% (342), Clostridium perfringens in 7% (90), and Shigella sonnei in 4% (46). The main mode of transmission was described as foodborne in 50% (642), over half of which were caused by salmonellas, and person to person in 39% (496), over half of which were caused by SRSV. Most outbreaks transmitted from person to person occurred in hospitals and in residential institutions for elderly people. Outbreaks lasted from one to 217 days (median five days) and their duration varied with the pathogen. The median attack rate was 37%. Illness was reported in 34,158 people, 751 of whom (2%) were admitted to hospital. There were 55 deaths, 28 of which were associated with salmonella and 12 with SRSV. Most of the outbreaks reported and the associated morbidity and mortality could have been prevented by following standard food hygiene practices, implementing infection control policies, and ensuring that food entering kitchens was of the highest microbiological quality possible.

The measles/rubella immunisation campaign in Scotland

This report describes why the 1994 measles/rubella immunisation campaign was necessary, reviews its implementation, and provides information on its impact in Scotland where 60,504 children were immunised. Data on suspected adverse reactions to the measles/rubella vaccine are also presented. A large UK measles epidemic was predicted by independent researchers, and action in response was planned in accordance with the recommendations of the Joint Committee on Vaccination and Immunisation. As a result, the epidemic predicted for England and Wales was averted and the epidemic which had occurred in the West of Scotland was prevented from spreading to the East. Laboratory-confirmed cases of measles and rubella are now rare in all parts of the UK, especially in the age group targeted by the campaign. Most reported adverse reactions were mild and self-limiting: only one child per 6,700 vaccinated in the UK was reported to have suffered any adverse reaction. Immediate, serious reactions were either allergic or were described as convulsions (most associated with immediate syncope); all of these children recovered fully. Later onset neurological problems were reported at rates no higher than expected from normal population incidence.

Outbreaks of infectious intestinal disease associated with person to person spread in hotels and restaurants

Twenty-eight outbreaks of infectious intestinal disease, reported as being transmitted mainly by the person to person route, were identified in association with retail catering premises, such as hotels, restaurants, and public houses, in England and Wales between 1992 and 1994. Five thousand and forty-eight people were at risk in these outbreaks and 1234 were affected. Most of the outbreaks (over 90%) occurred in hotels. Small round structured viruses were the most commonly detected pathogens. Diarrhoea and vomiting were common symptoms and most of the outbreaks occurred in the summer months. Control measures to contain infectious individuals and improved hygiene measures are necessary to contain such outbreaks.

The Public Health Laboratory Service national case-control study of primary indigenous sporadic cases of campylobacter infection

The aetiology of sporadic campylobacter infection was investigated by means of a multicentre case-control study. During the course of the study 598 cases and their controls were interviewed. Conditional logistic regressional analysis of the data collected showed that occupational exposure to raw meat (odds ratio [OR] 9.37; 95% confidence intervals [CI] 2.03, 43.3), having a household with a pet with diarrhoea (OR 2.39; CI 1.09, 5.25), and ingesting untreated water from lakes, rivers and streams (OR 4.16; CI 1.45, 11.9) were significant independent risk factors for becoming ill with campylobacter. Handling any whole chicken in the domestic kitchen that had been bought raw with giblets, or eating any dish cooked from chicken of this type in the home (OR 0.41-0.44; CI 0.24, 0.79) and occupational contact with livestock or their faeces (OR 0.44; CI 0.21, 0.92) were significantly associated with a decrease in the risk of becoming ill with campylobacter.

Outbreaks of foodborne infectious intestinal disease in England and Wales: 1992 and 1993

We have analysed data from the surveillance scheme of general foodborne outbreaks of infectious intestinal disease in England and Wales reported to, or otherwise identified by, the PHLS Communicable Disease Surveillance Centre in 1992 and 1993. Data were available about 458 outbreaks, 197 (43%) in commercial catering premises (restaurants, cafés, hotels, public houses, and canteens), 77 (17%) associated with food prepared in private houses, and 58 (13%) in hospitals and residential institutions. Salmonellas and Clostridium perfringens were responsible for 340 outbreaks (74%) and no pathogen was identified in 55 outbreaks (12%). Organisms associated with the highest mean attack rates were Staphylococcus aureus (66%) and C. perfringens (53%). Eleven thousand people were reported to be il and 362 were admitted to hospital. There were 15 deaths, 13 of which were associated with salmonellosis. A specified food was suspected to be the vehicle of infection in 204 outbreaks (45%). Possible contributory factors were identified in 277 (61%), most commonly inappropriate storage, cross contamination, and inadequate heat treatment. Reducing the incidence of food poisoning will depend on concerted action on farms, in abattoirs and food processing plants, in wholesale and retail outlets, and in kitchens.

Foodborne disease surveillance in England and Wales: 1989-1991

This review summarises reports of food poisoning, salmonellosis, campylobacteriosis and other acute foodborne illness to the PHLS Communicable Disease Surveillance Centre, and notifications of food poisoning collated by the Office of Population Censuses and Surveys, in the period 1989-1991. During this period there were continuing rises in notifications of food poisoning and reports of salmonellosis and campylobacteriosis. There was considerable success in the control of foodborne listeriosis. Newly emerging pathogens, such as Vero cytotoxin producing Escherichia coli, became more important. There was unprecedented scrutiny of the salmonella data by experts and politicians, reflecting continuing concern over the role of eggs as well as poultry meat in the increase of Salmonella enteritidis phage type 4 infection. This concern, along with advances in information technology, has led to developments in the collection and dissemination of information which continue to be implemented.

Infection with small round structured viruses: England and Wales 1981-1990

Infection with small round structured viruses (SRSV) usually causes an acute, but short-lived, attack of gastroenteritis in which vomiting is a prominent feature. Most documented outbreaks have occurred in institutional and catering establishments and infected food handlers are often implicated. Reports of SRSV infection have risen substantially during the last decade partly due to an increase in the number of laboratories able to examine samples for this organism. Ascertainment is likely to remain low, however, until a sensitive, simple, reliable and economical method of detection becomes routinely available.

A national outbreak of salmonellosis from yeast flavoured products

A national outbreak of salmonellosis caused by a rare serotype occurred between July and November 1989. A total of 40 cases of Salmonella manchester infection were identified by the PHLS Division of Enteric Pathogens with a further 7 cases reported from Scotland. The median age of those affected was one year. All strains from the outbreak carried a 70mDal plasmid with a distinctive restriction endonuclease. A statistical association was found between infection and consumption of nationally distributed savoury corn snacks. Samples of autolysed yeast powder and flavourings used in the manufacture of many processed foods were also found to be positive for S. manchester.

A national outbreak of Salmonella typhimurium DT 124 caused by contaminated salami sticks

An outbreak of Salmonella typhimurium DT 124 infection which affected 101 people in England in December 1987 and January 1988 was detected through surveillance of laboratory reports from medical microbiology laboratories of the NHS and PHLS. Within 1 week of noting the increase in reports, epidemiological and microbiological investigations identified a small German salami stick as the vehicle of infection and the product was withdrawn from sale. The epidemiological investigation highlighted the occurrence of a long incubation period, bloody diarrhoea. Prompt recognition and investigation of the outbreak prevented further cases of severe infection.

Case-control study of infections with Salmonella enteritidis phage type 4 in England

OBJECTIVE

To determine the source of indigenous sporadic infection with Salmonella enteritidis phage type 4.

DESIGN

Case-control study of primary sporadic cases identified by the Public Health Laboratory Service between 1 August and 30 September 1988.

SETTING

PHLS Communicable Disease Surveillance Centre, Division of Enteric Pathogens, 11 PHLS laboratories, and 42 local authority environmental health departments in England.

SUBJECTS

232 Patients (cases) with confirmed primary sporadic infection, for 160 of whom (88 female) (median age 30 years, age range 4 months to 85 years) data were obtained by questionnaire about consumption of fresh eggs, egg products, precooked chicken, and minced meat in the three days and one week before onset of the symptoms. Up to three controls, matched for neighbourhood, age, and sex (if aged greater than 11 years), were asked the same questions for the same calendar period.

MAIN OUTCOME MEASURE

Association of primary sporadic infection with consumption of suspected food items.

RESULTS

Illness due to S enteritidis phage type 4 was significantly associated with consumption of raw shell egg products (homemade mayonnaise, ice cream, and milk drinks containing eggs) (matched p = 0.02) and shop bought sandwiches containing mayonnaise (matched p = 0.00004) or eggs (matched p = 0.02). Illness was also significantly associated with eating lightly cooked eggs (unmatched p = 0.02), but not soft boiled eggs, and precooked hot chicken (matched p = 0.006). Reported consumption of eggs was not appreciably different between cases and controls before or after the median date of interview.

CONCLUSIONS

Fresh shell eggs, egg products, and precooked hot chicken are vehicles of S enteritidis phage type 4 infection in indigenous sporadic cases. Public health education and reduction in contamination of eggs and infection of poultry with S enteritidis are needed to reduce the incidence of human infection.

Two outbreaks of Salmonella enteritidis phage type 4 infection associated with the consumption of fresh shell-egg products

In 1988 there were two outbreaks of infection with Salmonella enteritidis phage type 4 in adjacent local authorities. The first affected 18 of 75 helpers and guests who attended a private function. Investigations revealed that home-made vanilla ice-cream containing uncooked eggs was the vehicle of infection and the causative organism was identified at the premises of the egg producer. The second affected 84 of 422 delegates attending a conference dinner, and 12 of 50 hotel staff at risk. A dessert made with lightly-cooked egg yolk and raw egg white was associated with infection, and the epidemic strain was cultured from the shell of an egg and an environmental sample from the producer's farm. It is of interest that one outbreak involved free-range and one battery-produced eggs, and that in one the vehicle was prepared at home and in the other in commercial premises. In neither incident was any deficiency in standards of egg production or catering practice discovered.