Using sequence data to identify alternative routes and risk of infection: a case-study of campylobacter in Scotland.

BACKGROUND: Genetic typing data are a potentially powerful resource for determining how infection is acquired. In this paper MLST typing was used to distinguish the routes and risks of infection of humans with Campylobacter jejuni from poultry and ruminant sources METHODS: C. jejuni samples from animal and environmental sources and from reported human cases confirmed between June 2005 and September 2006 were typed using MLST. The STRUCTURE software was used to assign the specific sequence types of the sporadic human cases to a particular source. We then used mixed case-case logistic regression analysis to compare the risk factors for being infected with C. jejuni from different sources. RESULTS: A total of 1,599 (46.3%) cases were assigned to poultry, 1,070 (31.0%) to ruminant and 67 (1.9%) to wild bird sources; the remaining 715 (20.7%) did not have a source that could be assigned with a probability of greater than 0.95. Compared to ruminant sources, cases attributed to poultry sources were typically among adults (odds ratio (OR) = 1.497, 95% confidence intervals (CIs) = 1.211, 1.852), not among males (OR = 0.834, 95% CIs = 0.712, 0.977), in areas with population density of greater than 500 people/km2 (OR = 1.213, 95% CIs = 1.030, 1.431), reported in the winter (OR = 1.272, 95% CIs = 1.067, 1.517) and had undertaken recent overseas travel (OR = 1.618, 95% CIs = 1.056, 2.481). The poultry assigned strains had a similar epidemiology to the unassigned strains, with the exception of a significantly higher likelihood of reporting overseas travel in unassigned strains. CONCLUSIONS: Rather than estimate relative risks for acquiring infection, our analyses show that individuals acquire C. jejuni infection from different sources have different associated risk factors. By enhancing our ability to identify at-risk groups and the times at which these groups are likely to be at risk, this work allows public health messages to be targeted more effectively. The rapidly increasing capacity to conduct genetic typing of pathogens makes such traced epidemiological analysis more accessible and has the potential to substantially enhance epidemiological risk factor studies.

Escherichia coli O157 infection and secondary spread, Scotland, 1999-2008.

To determine the proportion of Escherichia coli O157 cases in Scotland attributable to secondary spread, we analyzed data obtained through entire-population enhanced surveillance. We identified 11% of cases as secondary. Secondary cases in single households were younger than secondary cases in outbreaks affecting >1 household and had similar risk for hemolytic uremic syndrome.

Methods for determining disease burden and calibrating national surveillance data in the United Kingdom: the second study of infectious intestinal disease in the community (IID2 study).

BACKGROUND: Infectious intestinal disease (IID), usually presenting as diarrhoea and vomiting, is frequently preventable. Though often mild and self-limiting, its commonness makes IID an important public health problem. In the mid 1990s around 1 in 5 people in England suffered from IID a year, costing around pound0.75 billion. No routine information source describes the UK's current community burden of IID. We present here the methods for a study to determine rates and aetiology of IID in the community, presenting to primary care and recorded in national surveillance statistics. We will also outline methods to determine whether or not incidence has declined since the mid-1990s. METHODS/DESIGN: The Second Study of Infectious Intestinal Disease in the Community (IID2 Study) comprises several separate but related studies. We use two methods to describe IID burden in the community - a retrospective telephone survey of self-reported illness and a prospective, all-age, population-based cohort study with weekly follow-up over a calendar year. Results from the two methods will be compared. To determine IID burden presenting to primary care we perform a prospective study of people presenting to their General Practitioner with symptoms of IID, in which we intervene in clinical and laboratory practice, and an audit of routine clinical and laboratory practice in primary care. We determine aetiology of IID using molecular methods for a wide range of gastrointestinal pathogens, in addition to conventional diagnostic microbiological techniques, and characterise isolates further through reference typing. Finally, we combine all our results to calibrate national surveillance data. DISCUSSION: Researchers disagree about the best method(s) to ascertain disease burden. Our study will allow an evaluation of methods to determine the community burden of IID by comparing the different approaches to estimate IID incidence in its linked components.

Geographic determinants of reported human Campylobacter infections in Scotland.

BACKGROUND: Campylobacteriosis is the leading cause of bacterial gastroenteritis in most developed countries. People are exposed to infection from contaminated food and environmental sources. However, the translation of these exposures into infection in the human population remains incompletely understood. This relationship is further complicated by differences in the presentation of cases, their investigation, identification, and reporting; thus, the actual differences in risk must be considered alongside the artefactual differences. METHODS: Data on 33,967 confirmed Campylobacter infections in mainland Scotland between 2000 and 2006 (inclusive) that were spatially referenced to the postcode sector level were analysed. Risk factors including the Carstairs index of social deprivation, the easting and northing of the centroid of the postcode sector, measures of livestock density by species and population density were tested in univariate screening using a non-spatial generalised linear model. The NHS Health Board of the case was included as a random effect in this final model. Subsequently, a spatial generalised linear mixed model (GLMM) was constructed and age-stratified sensitivity analysis was conducted on this model. RESULTS: The spatial GLMM included the protective effects of the Carstairs index (relative risk (RR) = 0.965, 95% Confidence intervals (CIs) = 0.959, 0.971) and population density (RR = 0.945, 95% CIs = 0.916, 0.974. Following stratification by age group, population density had a significant protective effect (RR = 0.745, 95% CIs = 0.700, 0.792) for those under 15 but not for those aged 15 and older (RR = 0.982, 95% CIs = 0.951, 1.014). Once these predictors have been taken into account three NHS Health Boards remain at significantly greater risk (Grampian, Highland and Tayside) and two at significantly lower risk (Argyll and Ayrshire and Arran). CONCLUSIONS: The less deprived and children living in rural areas are at the greatest risk of being reported as a case of Campylobacter infection. However, this analysis cannot differentiate between actual risk and heterogeneities in individual reporting behaviour; nevertheless this paper has demonstrated that it is possible to explain the pattern of reported Campylobacter infections using both social and environmental predictors.

Emotional and behavioral changes in parents of children affected by hemolytic-uremic syndrome associated with verocytotoxin-producing Escherichia coli: a qualitative analysis.

BACKGROUND: The long-term clinical outcome for children affected by hemolytic uremic syndrome associated with verocytotoxin-producing Escherichia coli (VTEC-HUS) is well documented, but the parental experience is not. OBJECTIVE: The authors investigated the effects of the critical-care hospitalization for this condition on well-being of patients' families. METHOD: A group of 30 parents completed a free-response format survey when their child presented to the hospital; 19 of this cohort completed a 1-year follow-up. RESULTS: Content analysis demonstrated that this cohort of parents experienced long-term emotional distress and substantive disruption to family and daily life. DISCUSSION: These results corroborate anecdotal clinical observations. The authors suggest future research initiatives and best practices to reduce parental distress.

Overseas outbreaks of infectious intestinal disease identified in Scotland, 2003 to 2007.

BACKGROUND: This article presents information on all potential outbreaks of infectious intestinal disease (IID) identified by Health Protection Scotland (HPS) involving residents of Scotland. Unlike other systems, this alert system covers potential outbreaks of IID rather than apparently sporadic cases and covers all gastrointestinal pathogens, all visited countries, and all groups of travelers. METHODS: HPS collects information on all potential outbreaks of IID in residents of Scotland where infection is believed to have been acquired abroad and disseminates this to all public health teams in Scotland so other linked cases can be identified. Where possible HPS also disseminates the details to the national surveillance center in the country where infection is believed to have been acquired, enabling them to facilitate any investigations or control measures they believe necessary. The rate of outbreaks associated with travel to particular countries was determined using the number of visits reported for residents of Scotland from Travel Trends data from the Office of National Statistics. RESULTS: Between 2003 and 2007, 319 such potential outbreaks were identified. Spain was the most frequently identified country reflecting the fact that it was also the most frequently visited country; the rate per 100,000 visits to Spain was 1.4, very similar to the overall rate for all countries of 1.3, while the highest rate of 46.7 per 100,000 visitors was associated with travel to Egypt. Salmonella sp was the most frequently identified pathogen within which Salmonella enteritidis was the most frequently identified serotype. CONCLUSIONS: The system provides a rapid alert mechanism for potential outbreaks of IID outside Scotland, allowing their investigation and control as appropriate and demonstrates the risks of outbreaks associated with different countries and pathogens.

An evaluation of the risk assessment method used by Environmental Health Officers when inspecting food businesses.

Two outbreaks of infection with Salmonella enteritidis phage types 5c and 6a occurred in a number of Scottish health board areas between May 2000 and January 2001. A case-control study of food businesses was subsequently carried out to ascertain whether the scores derived from Environmental Health Officers' inspections prior to the outbreaks differed between food businesses where outbreak cases had eaten in the week before the onset of their illness (case food businesses) and neighbouring food businesses at which no outbreak case had eaten (control food businesses). The study showed no significant difference between the scores of case and control food businesses. The results suggest that the inspections were ineffective in identifying those food businesses that are more likely to cause incidents of food poisoning.