Preventing household transmission of Shiga toxin-producing Escherichia coli O157 (STEC O157) infection is important because of the ease of interpersonal transmission and the potential disease severity.
We conducted a retrospective cohort study of households associated with an outbreak of STEC O157 infection in South Wales, United Kingdom, in autumn 2005. We investigated whether characteristics of the primary case patient or the household were predictors for secondary household transmission of STEC O157 infection. Furthermore, we estimated the proportion of cases that might be prevented by isolation (e.g., hospitalization) of the primary case patient immediately after the microbiological diagnosis and the number of patients with STEC O157 who would need to be isolated to prevent 1 case of hemolytic uremic syndrome. Based on dates of symptom onset, case patients in households were classified as having primary, coprimary, or secondary infection. Secondary cases were considered to be preventable if the secondary case patient's symptoms started >1 incubation period (4 days) after the date of microbiological diagnosis of the primary case.
Eighty-nine (91%) of 98 eligible households were enrolled. Among 20 households (22%), 25 secondary cases were ascertained. Thirteen secondary cases (56%) occurred in siblings of the primary case patients; hemolytic uremic syndrome developed in 4 of these siblings. Presence of a sibling (risk ratio, 3.8; 95% confidence interval, 0.99-14.6) and young age (<5 years) of the primary case patient (risk ratio, 2.03; 95% confidence interval, 0.99-41.6) were independent predictors for households in which secondary cases occurred. Of the 15 secondary cases for which complete information was available, 7 (46%) might have been prevented. When restricting isolation to primary case patients who were aged <10 years and who had a sibling, we estimated the number of patients who would need to be isolated to prevent 1 case of hemolytic uremic syndrome to be 47 patients (95% confidence interval, 16-78 patients).
Promptly separating pediatric patients with STEC O157 infection from their young siblings should be considered.
"HUS cannot be prevented once an infection has been established. Preventing primary cases by removing the source of infection is obvious, but preventing secondary cases by promulgating hygiene messages to the public is crucially important.30 Second, there is more to inspecting an operation like a food business than ticking boxes. "
[Show abstract][Hide abstract] ABSTRACT: This review describes Escherichia coli O157 outbreaks in the United Kingdom, beginning from the first, in the 1980s, to those recorded in 2013. We point out that the United Kingdom differs from other countries, particularly the United States, in that it has had a considerable number of outbreaks associated with butchers, but very few caused by contaminated burgers. Two of the butcher-associated outbreaks (in central Scotland in 1996 and South Wales in 2005) were very large and are considered here in detail; the reviewer conducted detailed investigations into both outbreaks. Also considered is the very large outbreak that occurred in visitors to an open farm in Surrey in 2009. Detailed descriptions of some milk-borne outbreaks and incidents connected with camping and childrens' nurseries have been published, and these are also considered in this review. Large outbreaks in the United Kingdom have sometimes led to policy developments regarding food safety, and these are considered, together with public reactions to them, their health effect, and their value, as examples to follow or eschew in terms of the procedures to be adopted in response to incidents of this kind. Regulatory and legal consequences are also considered. As a wise man said, making predictions is difficult, particularly about the future. This review follows this position but points out that although human infections caused by E. coli O157 are rare in the United Kingdom, their incidence has not changed significantly in the last 17 years. This review points out that although a response to an outbreak is to say "lessons must be learned", this response has been tempered by forgetfulness. Accordingly, this review restricts its recommendations regarding outbreaks to two: the crucial importance of a rapid response and the importance of experience, and even "gut feeling", when an inspector is evaluating the safety of a food business.
Infection and Drug Resistance 08/2014; 7:211-22. DOI:10.2147/IDR.S49081
"Typically, young children who use the toilet independently but have limited understanding of good hand- and toilet-hygiene may be particularly susceptible to transmitting secondary infection. We did not find any increased risk among siblings of cases, or their mothers compared to other household contacts however, unlike similar research examining household transmission of E.Coli 0157 . Based on our findings, screening of all contacts of cases who are under 6 years is also recommended. "
[Show abstract][Hide abstract] ABSTRACT: Background
Internationally, guidelines to prevent secondary transmission of Shigella infection vary widely. Cases, their contacts with diarrhoea, and those in certain occupational groups are frequently excluded from work, school, or daycare. In the Netherlands, all contacts attending pre-school (age 0–3) and junior classes in primary school (age 4–5), irrespective of symptoms, are also excluded pending microbiological clearance. We identified risk factors for secondary Shigella infection (SSI) within households and evaluated infection control policy in this regard.
This retrospective cohort study of households where a laboratory confirmed Shigella case was reported in Amsterdam (2002–2009) included all households at high risk for SSI (i.e. any household member under 16 years). Cases were classified as primary, co-primary or SSIs. Using univariable and multivariable binomial regression with clustered robust standard errors to account for household clustering, we examined case and contact factors (Shigella serotype, ethnicity, age, sex, household size, symptoms) associated with SSI in contacts within households.
SSI occurred in 25/ 337 contacts (7.4%): 20% were asymptomatic, 68% were female, and median age was 14 years (IQR: 4–38). In a multivariable model adjusted for case and household factors, only diarrhoea in contacts was associated with SSI (IRR 8.0, 95% CI:2.7-23.8). In a second model, factors predictive of SSI in contacts were the age of case (0–3 years (IRRcase≥6 years:2.5, 95% CI:1.1-5.5) and 4–5 years (IRRcase≥6 years:2.2, 95% CI:1.1-4.3)) and household size (>6 persons (IRR2-4 persons 3.4, 95% CI:1.2-9.5)).
To identify symptomatic and asymptomatic SSI, faecal screening should be targeted at all household contacts of preschool cases (0–3 years) and cases attending junior class in primary school (4–5 years) and any household contact with diarrhoea. If screening was limited to these groups, only one asymptomatic adult carrier would have been missed, and potential exclusion of 70 asymptomatic contacts <6 years old from school or daycare, who were contacts of cases of all ages, could have been avoided.
"Interestingly, having contact with a child under 5 years old emerged as a risk factor for seroprevalence by unadjusted analysis. A previous study by Belongia et al. (2003) showed that levels of E. coli O157 antibodies in farm-resident children (particularly the under fives) were significantly higher than non-farm-resident children, and Werber et al. (2008) "
[Show abstract][Hide abstract] ABSTRACT: Evidence suggests that frequent and direct exposure to domestic animals has made farmers less susceptible to symptomatic Escherichia coli O157 infection than other members of the community. We have quantified the seroprevalence of antibodies to E. coli O157 lipopolysaccharide (LPS) from a representative cohort of farm workers in three geographically distinct regions of the United Kingdom during two sampling rounds over a 2-year period. All participants completed a questionnaire to determine the range and extent of recent animal contact alongside other potential occupational and environmental exposure routes. A total of 31/946 (3.3%) serum samples contained antibodies to E. coli O157 LPS (from both rounds combined). On the second sampling round, a significant difference in seropositivity was apparent between the three regions, with enhanced seroprevalence linked to recent contact with beef cattle, having a private water supply and contact with a child under 5 years old. Only five seropositive people reported symptoms of a gastrointestinal tract infection, although these symptoms were mild. These results further support the premise of acquired immunity to E. coli O157 associated with prolonged antigenic exposures within the farming environment.
Zoonoses and Public Health 08/2011; 59(2):83-8. DOI:10.1111/j.1863-2378.2011.01430.x · 2.37 Impact Factor
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