General outbreaks of infectious intestinal diseases linked with private residences in England and Wales, 1992-9: questionnaire studyBMJ 2001; 323 doi: https://doi.org/10.1136/bmj.323.7321.1097 (Published 10 November 2001) Cite this as: BMJ 2001;323:1097
- Iain A Gillespie, clinical scientist,
- Sarah J O'Brien, consultant epidemiologist (, )
- Goutam K Adak, principal scientist
- Gastrointestinal Diseases Division, Public Health Laboratory Service Communicable Disease Surveillance Centre, London NW9 5EQ
- Correspondence to: S J O'Brien
- Accepted 2 May 2001
The inception of the Food Standards Agency in April 2000 has given food safety issues a high public and political profile. Recently, concerns about food hygiene have focused on the home and, in particular, the possible transmission of infection via household items.1 To determine the causes of gastrointestinal infection associated with the home, we reviewed general outbreaks (outbreaks affecting more than one household) of infectious intestinal disease in England and Wales reported to the Public Health Laboratory Service (PHLS) Communicable Disease Surveillance Centre from 1992 to 1999.
Methods and results
After initial outbreaks of infectious intestinal disease in England and Wales the centre obtained data via a standard, structured questionnaire (response rate >80%)2 and stored it in a dynamic database derived from EpiInfo version 5. We selected outbreaks linked with private households and analysed them with Microsoft Excel and Stata version 6. Relative proportions of outbreak settings and types were compared using the χ2 test.
General outbreaks in the home (figure) accounted for 226 (5%) of the 4604 outbreaks reported during the surveillance period; of 4602 people affected, 205 (4.5%) were admitted to hospital. The risk of hospitalisation from outbreaks linked to the home was higher than that linked with outbreaks related to other premises (0.045 v 0.016; risk ratio 2.66; 95% confidence interval 2.31 to 3.06).
Food was the predominant transmitter of infectious intestinal disease (192/226; 85%); person to person transmission (13; 6%) and waterborne transmission (3; 1%) accounted for some of the remainder. The mode of transmission was unknown in 9 (4%) outbreaks. Foodborne transmission was linked to social functions—for example, barbecues and dinner parties—more frequently than other modes of transmission were (169/192 (88%) v 17/34 (50%); χ2=28.5, df=1, P<0.001). The mean size of group affected was 20 people (range 2 to 224, median 12, mode 8). The most frequently reported pathogen was salmonella (147/192; 77%); Clostridium perfringens (9; 5%), Norwalk-like virus (8; 4%), and Vero cytotoxin producing Escherichia coli O157 (3; 2%) featured less often. Poultry (59/207; 29%), desserts (37; 18%)—which often contained raw egg—and egg dishes (35; 17%) were commonly implicated; the link between these food vehicles and salmonella is well understood.3 The most common faults in food hygiene were inappropriate storage, inadequate cooking, and cross contamination (99/251, 39%; 78, 31%; and 51, 20%, respectively); in each case salmonella was reported more frequently than any other pathogen (84/99, 85%; 67/78, 86%; and 43/51, 84%, respectively). Inappropriate storage was more commonly reported as a food hygiene fault in homes than in other premises (99/251 (39%) v 343/1309 (26%); χ2=18.2, df=1, P<0.001).
The downward trend in general outbreaks of infectious intestinal disease linked with the home reflects the national fall in outbreaks of salmonellosis. Foodborne outbreaks in the home seemed to occur when individuals catered for larger groups than usual. However, the surveillance system favours the inclusion of these outbreaks as large outbreaks are more likely to be identified and reported. Our analysis found much evidence that the outbreaks are related to cross contamination in the kitchen and this is supported by experiments that show how easy it is for the environment to be contaminated.4
The downward trend in general outbreaks linked with the home is encouraging and mirrors the national decrease in salmonella infection, which is probably due, at least in part, to the vaccination of poultry flocks. Lowering the risk of introducing salmonella into the home seems to benefit the consumer. Thus, it seems that the food industry can also make a positive contribution to reducing foodborne outbreaks.
We thank the consultants in communicable disease control, public health physicians, microbiologists, environmental health officers, infection control nurses, and all the staff at the PHLS and NHS laboratories who contribute to this surveillance system, and Mrs S Le Baigue and Miss S Long who maintain the database at CDSC. We also thank Dr R T Mitchell for his helpful comments on the manuscript and Catriona Graham for statistical advice.
Contributors: SJO'B initiated the work. IAG performed the statistical analyses. SJO'B, IAG, and GKA all contributed to the drafting of the paper. SJO'B will act as the guarantor.
Competing interests None declared.
See the BMJ's website for more data on coronary artery grafts 1981-96