Outbreaks of waterborne infectious intestinal disease in England and Wales, 1992-2003.

We reviewed the epidemiological and microbiological characteristics of 89 reported outbreaks of waterborne infectious intestinal disease affecting 4321 people in England and Wales over the period 1992-2003. Public water supplies were implicated in 24 outbreaks (27%), private water supplies in 25 (28%), swimming pools in 35 (39%) and other sources in five outbreaks (6%). Cryptosporidium was implicated in 69% of outbreaks, Campylobacter sp. in 14%, Giardia in 2%, E. coli O157 in 3% and Astrovirus in 1%. From 2000, there was a consistent decline in the number of outbreaks of waterborne disease associated with public water supplies. The incidence rate of outbreaks in recipients of private water supplies may be as high as 35 times the rate in those receiving public water supplies (1830 vs. 53 per million population). Private water suppliers need to be aware of the importance of adequate treatment and the prevention of faecal contamination of storage water. Swimming-pool operators need to ensure chlorination and in particular adequate filtration measures are in place.

Listeria monocytogenes and listeriosis: a review of hazard characterisation for use in microbiological risk assessment of foods.

Considerable effort has been put into the application of quantitative microbiological risk assessment for Listeria monocytogenes, and data are available for England and Wales (probably more so than most other countries) on the adverse health effects, together with incidence data on different age and risk groups for human L. monocytogenes infections. This paper reviews aspects of Listeria and human listeriosis, especially from a public health perspective and provide hazard characterisation data, i.e. the qualitative and/or quantitative evaluation of the adverse health effect associated with the hazard, which is the relationship between exposure levels (dose) and frequency of illness. The majority of cases of human listeriosis are food-borne; however, the disease process is complex with multiple routes of infection. The dose-response relationship is poorly understood, and data from human volunteer studies are not available and would be unethical to produce. Data are available from a range of different animal and in vitro models, although these poorly mimic the natural disease process in route of infection, end point, host and history of prior exposure to the bacterium. Epidemiological data provide some information on infective doses and dose responses, but because of the characteristics of the disease (the hugely variable and potentially very long incubation periods, the low attack rates and the rarity of identification of specific food vehicles), this also provides limited data for calculation of dose responses. There is some, albeit limited, evidence for strain variation, but this is an area of considerable uncertainty despite great advances in the genetic basis of the virulence of this bacterium, and almost all strains seem capable of causing serious disease. A variety of mathematical approaches have been used to model dose responses. The review is written to provide a clinical and epidemiological background to the mathematically oriented, as well as to outline the mathematical approaches to those interested in food-borne infection.

Surveillance of listeriosis in England and Wales, 1995-1999.

A total of 543 cases of listerIosis were ascertained by the Public Health Laboratory Service Communicable Disease Surveillance Centre (PHLS CDSC) in residents of England and Wales with onset of illness between 1st January 1995 and 31st December 1999. Of 452 non-pregnancy associated cases, 326 (72%) had major medical conditions, 140 (31%) had received immuno-suppressive therapy and 97 (21%) were aged 60 years or over. Serovar 4b predominated in both pregnancy and non-pregnancy associated cases. Of ninety-one pregnancy associated cases, five had underlying medical conditions. Foetal death or early neonatal death was reported in 24 (26%) of the cases giving a mean perinatal mortality rate of 7.5 per million conceptions per year. Two episodes of neonatal cross infection occurred. Two non-pregnancy associated cases in 1999 were linked by a common food; all other cases were unlinked. No trend was observed from 1995 to 1999.

General outbreaks of infectious intestinal disease linked with red meat, England and Wales, 1992-1999.

Between 1992 and 1999, 1,426 foodborne general outbreaks of infectious intestinal disease (IID) were reported to the Public Health Laboratory Service (PHLS) Communicable Disease Surveillance Centre (CDSC). Sixteen percent were linked with the consumption of red meat. Over 5,000 people were affected, with 186 hospital admissions and nine deaths. Beef (34%) and pig meat (32%) were the most frequently implicated meat types, with lamb implicated in 11% of outbreaks. The organisms most frequently reported were Clostridium perfringens (43.4%) and salmonellas (34.3%). During the summer, outbreaks were mainly of Salmonella spp. and attributed to the consumption of pig meat. In December, outbreaks of C. perfringens linked with beef predominated. Most outbreaks occurred as a result of food cooked on commercial catering premises (46%). The highlight of this surveillance period is a fall in the number of outbreaks linked with foods containing red meat. This corresponds with a steady decline in red meat consumption over the last two decades, as well as a transient though marked decline in the purchase and consumption of red meat in the UK during the BSE crisis in the early to mid 1990s. As cited in the Pennington Report, further reducing the morbidity and mortality from red meat outbreaks means targeting meat production at various points along the food chain from abattoir and butchering, to cooking and holding of cooked food, especially on commercial catering premises.