Publications (13)65.98 Total impact
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Article: The "case-chaos study" as an adjunct or alternative to conventional case-control study methodology.
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ABSTRACT: Case-control studies are important in infectious disease epidemiology for rapidly identifying and controlling risks, but challenges, including the need for speed, can place practical restrictions on control selection and recruitment. The biased comparisons that result can hamper or, worse, mislead investigators. Following a 2009 outbreak of Shiga-like toxin-producing Escherichia coli O157 infection associated with a petting farm in southeast England, it was hypothesized that case behavior alone could be used to identify risks. Case-patients' exposures were randomized on a case-by-case basis, and the resulting permuted data were compared with the actual events preceding illness by conditional logistic regression analysis. There was good agreement between the risks identified by using our new method and the risks elicited in the original outbreak case-control studies. This was also the case in analysis of 2 further historical outbreaks. These initial findings suggest that the technique, which we have called the "case-chaos" technique, appeared to be useful in this setting. Analysis of simulated data supports this view. Circumventing the need for traditional control data has the potential to reduce outbreak investigation lead times, leading to earlier interventions and reduced morbidity and mortality. However, further validation is necessary, coupled with an awareness of limitations of the method.American journal of epidemiology 08/2012; 176(6):497-505. · 5.59 Impact Factor -
Article: Concurrent conditions and human listeriosis, England, 1999-2009.
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ABSTRACT: The epidemiology of listeriosis in England and Wales changed during 2001-2008; more patients ≥60 years of age had bacteremia than in previous years. To investigate these changes, we calculated risk for listeriosis by concurrent condition for non-pregnancy-associated listeriosis cases reported to the national surveillance system in England during 1999-2009. Conditions occurring with L. monocytogenes infection were coded according to the International Classification of Diseases, 10th Revision, and compared with appropriate hospital episode statistics inpatient denominator data to calculate incidence rates/million consultations. Malignancies (especially of the blood), kidney disease, liver disease, diabetes, alcoholism, and age ≥60 years were associated with an increased risk for listeriosis. Physicians should consider a diagnosis of listeriosis when treating patients who have concurrent conditions. Providing cancer patients, who accounted for one third of cases, with food safety information might help limit additional cases.Emerging Infectious Diseases 01/2011; 17(1):38-43. · 6.79 Impact Factor -
Article: Listeria monocytogenes infection in the over-60s in England between 2005 and 2008: a retrospective case-control study utilizing market research panel data.
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ABSTRACT: A retrospective case-control study of listeriosis in patients in England aged over 60 years is described. The incidence of listeriosis in patients aged ≥60 years in England has doubled since 2001; hence, the investigation of risk factors for infection in this group is important to inform on prevention and control. Standardized epidemiological information has been sought on cases since 2005, but the value of the data accrued is limited without some perception of exposure prevalence in the population at risk of listeriosis. The exposures of listeriosis cases aged ≥60 years reported in England from 2005 to 2008 were compared to those of market research panel members representing the same population (i.e., residents of England aged ≥60 years) and time period. Exposures were grouped to facilitate comparison. Odds ratios and 95% confidence intervals were calculated. Cases were more likely than panel members to report the consumption of cooked meats (beef and ham/pork, but not poultry), cooked fish (specifically smoked salmon) and shellfish (prawns), dairy products (most noticeably milk but also certain cheeses), and mixed salads. They were less likely to report the consumption of other forms of seafood, dairy spread, other forms of dairy, sandwiches, and fresh vegetables. The diversity of high-risk food exposures reflects the ubiquity of the microorganism in the environment and/or the susceptibility of those at risk, and suggests that a wider variety of foods can give rise to listeriosis. Food safety advice on avoiding listeriosis should be adapted accordingly. While not inexpensive, the application of market research data to infectious disease epidemiology can add value to routine surveillance data.Foodborne Pathogens and Disease 11/2010; 7(11):1373-9. · 2.26 Impact Factor -
Article: Attribution of human Listeria monocytogenes infections in England and Wales to ready-to-eat food sources placed on the market: adaptation of the Hald Salmonella source attribution model.
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ABSTRACT: Human listeriosis is a rare but serious foodborne disease, with high morbidity and mortality in vulnerable populations (e.g., pregnant women, the elderly, and the immunocompromised). The disease is predominantly caused by the consumption of contaminated ready-to-eat foods. Since 2001, an increase in the number of listeriosis cases has been observed in several European Union countries, including England and Wales, predominantly in the over-60s population. The cause of this selective increased incidence is unknown. The Hald Salmonella Bayesian source attribution model was adapted to determine the potential of this approach to quantify the contribution of different food sources to the burden of human listeriosis in England and Wales from 2004 to 2007. The most important food sources for the overall population were multicomponent foods (sandwiches and prepacked mixed salad vegetables) (23.1%), finfish (16.8%), and beef (15.3%). Attribution of major sources of infection was similar for the elderly population (>or=60 years old, multicomponent foods [22.0%], finfish [14.7%], and beef [13.6%]). For pregnancy-associated cases, beef (12.3%), milk and milk products (11.8%), and finfish (11.2%) were more important sources of infection. The adapted model also showed that the serotype 4b was associated with relatively more human infections than that of other serotypes; further, the subtype 4b amplified fragment-length polymorphism V was associated with more pregnancy-associated cases than other subtypes of 4b. This approach of quantifying the contribution of various food sources to human listeriosis provides a useful tool in food safety risk analysis, and underlines the need for further emphasis to be given to the reduction of Listeria monocytogenes in high-risk foods, such as multicomponent foods, which are consumed without any further treatment. The need for targeted dietary advice for the elderly population is also highlighted.Foodborne Pathogens and Disease 02/2010; 7(7):749-56. · 2.26 Impact Factor -
Article: Age patterns of persons with campylobacteriosis, England and Wales, 1990-2007.
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ABSTRACT: To explore hypotheses for age-related changes in the incidence of Campylobacter infections in England and Wales during 1990-2007, we analyzed electronic laboratory data. Disease incidence was reduced among children, and the greatest increase in risk was for those >/=60 years of age. Risk factors for campylobacteriosis in the elderly population should be identified.Emerging Infectious Diseases 12/2009; 15(12):2046-8. · 6.79 Impact Factor -
Article: Disease presentation in relation to infection foci for non-pregnancy-associated human listeriosis in England and Wales, 2001 to 2007.
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ABSTRACT: Listeriosis is a rare but severe food-borne disease, affecting unborn or newly delivered infants, the elderly, and the immunocompromised. The epidemiology of listeriosis in England and Wales changed between 2001 and 2007, with more patients > or = 60 years old presenting with bacteremia (but without central nervous system [CNS] involvement). In order to explain this increase and understand the altered disease presentation, clinical, microbiological, and seasonal data on bacteremic cases of Listeria monocytogenes infection identified through national surveillance were compared with those for patients with CNS infections. Logistic regression analysis was applied while controlling for age. Bacteremic patients, who presented more frequently with gastrointestinal symptoms, were more likely to have underlying medical conditions than CNS patients. This was most marked in patients with malignancies, particularly digestive organ malignancies. Treatment to reduce stomach acid secretion modified the effect of nonmalignant underlying conditions on outcome, i.e., patients with an underlying condition who were not taking acid-suppressing medication were equally likely to have a bacteremic or a CNS infection. However, this type of therapy did not modify the effect of malignancies on the likelihood of having a bacteremic or a CNS infection. The increase in the incidence of human listeriosis among patients > or = 60 years old in England and Wales between 2001 and 2007 appears to have occurred in those with cancer or other conditions whose treatment included acid-suppressing medication. Therefore, this vulnerable patient group needs specific dietary advice on avoiding risk factors for listeriosis.Journal of clinical microbiology 09/2009; 47(10):3301-7. · 4.16 Impact Factor -
Article: Changing pattern of human listeriosis, England and Wales, 2001-2004.
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ABSTRACT: Microbiologic and epidemiologic data on 1,933 cases of human listeriosis reported in England and Wales from 1990 to 2004 were reviewed. A substantial increase in incidence occurred from 2001 to 2004. Ten clusters (60 cases), likely to represent common-source outbreaks, were detected. However, these clusters did not account for the upsurge in incidence, which occurred sporadically, predominantly in patients > or =60 years of age with bacteremia and which was independent of sex; regional, seasonal, ethnic, or socioeconomic differences; underlying conditions; or Listeria monocytogenes subtype. The reasons for the increase are not known, but since multiple L. monocytogenes strains were responsible, this upsurge is unlikely to be due to a common-source outbreak. In the absence of risk factors for listeriosis in this emerging at-risk sector of the population, dietary advice on avoiding high-risk foods should be provided routinely to the elderly and immunocompromised, not just to pregnant women.Emerging infectious diseases 09/2006; 12(9):1361-6. · 6.17 Impact Factor -
Article: Investigating vomiting and/or bloody diarrhoea in Campylobacter jejuni infection.
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ABSTRACT: Campylobacter jejuni infection frequently presents as acute enteritis with diarrhoea, malaise, fever and abdominal pain. Vomiting and bloody diarrhoea are reported less frequently. To investigate potential host, micro-organism or environmental factors that might explain the different clinical presentations, the features of laboratory-confirmed Campylobacter jejuni cases presenting with vomiting and/or bloody diarrhoea were compared with cases who did not report either clinical manifestation. Single variable analysis and logistic regression were employed. Explanatory variables included food, water and environmental risks. Cases who reported vomiting and/or bloody diarrhoea tended to suffer a longer illness and were more likely to require hospital admission. Independent risks identified were being a child, female gender, consumption of poultry other than chicken, pre-packed sandwiches and sausages, and reported engineering work or problems with drinking-water supply. A dose-response relationship with vomiting and/or bloody diarrhoea and increasing daily consumption of unboiled tap water was observed also. Vomiting and/or bloody diarrhoea characterized the more severe end of the disease spectrum and might relate to host susceptibility and/or infective dose. The role of unboiled tap water as a potential source of C. jejuni infection in England and Wales requires further investigation.Journal of Medical Microbiology 07/2006; 55(Pt 6):741-6. · 2.50 Impact Factor -
Article: Is Campylobacter jejuni enteritis a weekend disease?
Journal of Infection 05/2005; 50(3):265-7. · 4.13 Impact Factor -
Article: Childhood hemolytic uremic syndrome, United Kingdom and Ireland.
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ABSTRACT: We conducted prospective surveillance of childhood hemolytic uremic syndrome (HUS) from 1997 to 2001 to describe disease incidence and clinical, epidemiologic and microbiologic characteristics. We compared our findings, where possible, with those of a previous study conducted from 1985 to 1988. The average annual incidence of HUS for the United Kingdom and Ireland (0.71/100,000) was unchanged from 1985 to 1988. The overall early mortality had halved, but the reduction in mortality was almost entirely accounted for by improved outcome in patients with diarrhea-associated HUS. The principal infective cause of diarrhea-associated HUS was Shiga toxin-producing Escherichia coli O157 (STEC O157), although in the 1997-2001 survey STEC O157 phage type (PT) 21/28 had replaced STEC O157 PT2 as the predominant PT. The risk of developing diarrhea-associated HUS was significantly higher in children infected with STEC O157 PT 2 and PT 21/28 compared with other PTs. Hypertension as a complication of HUS was greatly reduced in patients with diarrhea-associated HUS.Emerging infectious diseases 05/2005; 11(4):590-6. · 6.17 Impact Factor -
Article: Temperature-driven Campylobacter seasonality in England and Wales.
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ABSTRACT: Campylobacter incidence in England and Wales between 1990 and 1999 was examined in conjunction with weather conditions. Over the 10-year interval, the average annual rate was determined to be 78.4 +/- 15.0 cases per 100,000, with an upward trend. Rates were higher in males than in females, regardless of age, and highest in children less than 5 years old. Major regional differences were detected, with the highest rates in Wales and the southwest and the lowest in the southeast. The disease displayed a seasonal pattern, and increased campylobacter rates were found to be correlated with temperature. The most marked seasonal effect was observed for children under the age of 5. The seasonal pattern of campylobacter infections indicated a linkage with environmental factors rather than food sources. Therefore, public health interventions should not be restricted to food-borne approaches, and the epidemiology of the seasonal peak in human campylobacter infections may best be understood through studies in young children.Applied and Environmental Microbiology 02/2005; 71(1):85-92. · 3.83 Impact Factor -
Article: A case-case comparison of Campylobacter coli and Campylobacter jejuni infection: a tool for generating hypotheses.
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ABSTRACT: Preventing campylobacteriosis depends on a thorough understanding of its epidemiology. We used case-case analysis to compare cases of Campylobacter coli infection with cases of C. jejuni infection, to generate hypotheses for infection from standardized, population-based sentinel surveillance information in England and Wales. Persons with C. coli infection were more likely to have drunk bottled water than were those with C. jejuni infection and, in general, were more likely to have eaten pâté. Important differences in exposures were identified for these two Campylobacter species. Exposures that are a risk for infection for both comparison groups might not be identified or might be underestimated by case-case analysis. Similarly, the magnitude or direction of population risk cannot be assessed accurately. Nevertheless, our findings suggest that case-control studies should be conducted at the species level.Emerging infectious diseases 10/2002; 8(9):937-42. · 6.17 Impact Factor -
Article: Campylobacter species: don't put all your eggs in one chicken.
Clinical Infectious Diseases 04/2002; 34(5):719-20. · 9.15 Impact Factor
Top co-authors
Top Journals
Institutions
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2005–2011
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Health Protection Agency
- • Gastrointestinal, Emerging and Zoonotic Infections (GEZI) department
- • Health Protection Agency - North East
London, ENG, United Kingdom
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2009
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The University of Manchester
Manchester, ENG, United Kingdom
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