Near real-time space-time cluster analysis for detection of enteric disease outbreaks in a community setting

OBJECTIVES

To enhance timely surveillance of bacterial enteric pathogens, space-time cluster analysis was introduced in Israel in May 2013.

METHODS

Stool isolation data of Salmonella, Shigella, and Campylobacter from patients of a large Health Maintenance Organization were analyzed weekly by ArcGIS and SaTScan, and cluster results were sent promptly to local departments of health (LDOHs).

RESULTS

During eighteen months, we identified 52 Shigella sonnei clusters, two Salmonella clusters, and no Campylobacter clusters. S. sonnei clusters lasted from one to 33 days and included three to 30 individuals. Thirty-one (60%) of the S. sonnei clusters were known to LDOHs prior to cluster analysis. Clusters not previously known by the LDOHs prompted epidemiologic investigations. In 31 of the 37 (84%) confirmed clusters, educational institutes (nursery schools, kindergartens, and a primary school) were involved.

CONCLUSIONS

Cluster analysis demonstrated capability to complement enteric disease surveillance. Scaling up the system can further enhance timely detection and control of outbreaks.

[Shigella sonnei outbreak in a school in Northern Spain]

In October 2012, an outbreak of acute gastroenteritis caused by Shigella sonnei was detected in a nursery and primary school in the north of Spain affecting 112 people: 63.7% were pupils and teachers and 35.7% their co-habitants. The source was a sick child who had travelled to an endemic country, and the key trigger factor was inadequate hygiene in one of the toilets of the school. The enforcement of strict hygiene measures was essential for controlling the outbreak.

Risk factors for secondary transmission of Shigella infection within households: implications for current prevention policy

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.

Methods

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.

Results

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 (IRR_{case≥6 years}:2.5, 95% CI:1.1-5.5) and 4–5 years (IRR_{case≥6 years}:2.2, 95% CI:1.1-4.3)) and household size (>6 persons (IRR_{2-4 persons} 3.4, 95% CI:1.2-9.5)).

Conclusions

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.

Shigellosis outbreak linked to canteen-food consumption in a public institution: a matched case-control study

On 13 November 2009, the authorities of Flemish Brabant, Belgium, received an alert concerning a potential outbreak of Shigella sonnei at a public institution. A study was conducted to assess the extent, discover the source and to implement further measures. We performed a matched case-control study to test an association between shigellosis and canteen-food consumption. Water samples and food handlers' faecal samples were tested. The reference laboratory characterized the retrospectively collected Shigella specimens. We found 52 cases distributed over space (25/35 departments) and time (2 months). We found a matched odds ratio of 3·84 (95% confidence interval 1·02-14·44) for canteen-food consumption. A food handler had travelled to Morocco shortly before detection of the first laboratory-confirmed case. Water samples and food handlers' faecal samples tested negative for Shigella. Confirmed cases presented PFGE profiles, highly similar to archived isolates from Morocco. Foodborne transmission associated with the canteen was strongly suspected.

A review of gastrointestinal outbreaks in schools: effective infection control interventions

BACKGROUND

The purpose of this study was to review documented outbreaks of gastrointestinal illness in schools, published in the last 10 years, to identify etiology, mode of transmission, the number of children affected, morbidity and mortality patterns, and interventions for control and prevention.

METHODS

Searches of electronic databases, public health publications, and federal, state, and provincial public health Web sites were completed.

RESULTS

Of the 121 outbreaks that met the inclusion criteria, 51% were bacterial, 40% viral, 7% were from Cryptosporidium, and 2% from multiple organisms. Transmission routes recorded in 101 reports included foodborne (45%), person-to-person (16%), waterborne (12%), and animal contact (11%). Actions to control outbreaks included alerting medical and public health authorities or the community to the outbreak (13%), treating cases (12%), enhancing hand washing (11%), and increased vigilance during food preparation (8%). Recommendations to prevent future outbreaks were compared with previously published studies that demonstrated effectiveness.

CONCLUSIONS

The risk of foodborne illness was reduced when food handlers practiced effective hand washing technique and received food safety training and certification. Student training programs on hand hygiene, enhanced cleaning and disinfection of the school, and hepatitis A vaccination were found effective. Children should be supervised on farm visits, hand washing strictly enforced, and food eaten in an area separated from the animals. Staff and students should have a positive, continuous communication with public health authorities including educational sessions and immediate reporting of possible outbreaks.

The health impacts of heat waves in five regions of New South Wales, Australia: a case-only analysis

OBJECTIVES

To determine and characterise the health impacts of extreme heat events on the population in five regions of New South Wales (NSW). Such data provide evidence necessary for the development of policy and programme initiatives designed to reduce the burden of disease due to the impact of climate change.

METHODS

A case-only approach was used to analyse 1,497,655 emergency hospital admissions in Sydney East and West, Illawarra, Gosford-Wyong and Newcastle. The distribution of daily minimum and maximum temperatures in each region was used to define extreme heat (≥99th percentile). We investigated the susceptibility of the main causes of emergency hospital admission to extreme heat. We also examined the presence of underlying conditions as a risk modifier of emergency hospital admission on extreme heat. Logistic regression model was used to estimate the effect modifications.

RESULTS

Main causes: On days of extreme heat, the risk of emergency hospital admission due to heat-related injuries, dehydration and other disorders of fluid, electrolyte and acid-base balance increased more than the risk of admission from other causes. Underlying conditions: Those with underlying mental and behavioural disorders, diseases of nervous and circulatory system, especially cardiac, diseases of respiratory system, especially asthma and chronic obstructive pulmonary disease, neoplasms and renal disease, especially renal failure, were more susceptible to an extreme heat event.

CONCLUSIONS

In this study, we identified several main diagnoses and underlying conditions for emergency hospital admission that are particularly susceptible to extreme heat events. This knowledge can contribute directly to establishing health programmes that would effectively target those with higher relative risk of emergency hospital admission due to extreme heat.

Transmission risk factors and treatment of pediatric shigellosis during a large daycare center-associated outbreak of multidrug resistant Shigella sonnei: implications for the management of shigellosis outbreaks among children

BACKGROUND

Shigellosis outbreaks in daycare centers result in substantial disease and economic burdens in the United States. The emergence of multidrug resistant Shigella strains raises questions regarding control of transmission within daycare centers and treatment for children. From May to October 2005, 639 Shigella sonnei cases were reported in northwest Missouri, mostly among persons exposed to daycare centers.

METHODS

We conducted a case-control investigation among licensed daycare centers (LDCs) in northwest Missouri to determine transmission risk factors, tested isolates for antimicrobial resistance, and described treatment practices. Case LDCs had secondary attack rates of shigellosis>or=2% (range, 2%-25%) and control LDCs<or=2% (range, 0%-1.3%). We interviewed LDC staff and performed on-site inspections. Thirty-one outbreak isolates were tested for antimicrobial resistance. We interviewed physicians and reviewed health department outbreak-related treatment data.

RESULTS

We enrolled 18 case and 21 control LDCs. LDCs with >or=1 sink in every room (odds ratio [OR]: 0.1; 95% confidence interval [CI]: 0.02-0.5) or a diapering station in every room (OR: 0.1; 95% CI: 0.01-0.6) were less likely to be case-LDCs. Resistance to ampicillin and trimethoprim-sulfamethoxazole was found in 90% of the outbreak strains. Among 210 children treated with antimicrobial agents, azithromycin was used in 92 (44%) while a fluoroquinolone was used in 11 (5%) children.

CONCLUSIONS

During a large daycare center-associated shigellosis outbreak, strains were highly resistant to ampicillin and trimethoprim-sulfamethoxazole. Children were frequently treated with azithromycin and occasionally fluoroquinolones. Appropriate handwashing and diapering infrastructure are necessary to minimize spread of shigellosis within daycare centers, and could reduce use of antimicrobial agents.

[Shigella spp. infections in Getafe Hospital between 2001 and 2006]

INTRODUCTION

Shigella spp. is a bacterium that frequently causes diarrhoea in underdeveloped countries, but not so much in Spain, where it has been published that its incidence has decreased in the last few years.

OBJECTIVE

The aim of this study has been to asses changes in the epidemiology of Shigella spp. infection over the last 5 years in children of Getafe, as well as the subspecies of Shigella spp. that cause illness in this area (area 10, Madrid), the need for hospitalisation, the complications and the treatment.

METHOD

A retrospective study was carried out, based on a review of the medical charts of children less than fifteen years old and had a diagnosis of Shigella spp. infection during 2000-2006. They were identified through the Getafe Hospital Microbiology Service.

RESULTS

Nineteen patients were identified, of which only four needed to be hospitalised. There were no differences between males and females. The Shigella spp. subspecies identified were S. sonnei and S. flexneri. The most frequent symptoms were vomiting, abdominal pain, diarrhoea, and fever. Only one had dehydration as a complication. The treatment was symptomatic, except in the four hospitalised patients, who required fluid therapy and antibiotics. The outcome was good in all patients.

CONCLUSION

In this study, there appears to be an increase in the Shigella spp. incidence over the last few years in Area 10 of Madrid. Due to the fact that Shigella spp. is not a frequent bacterium in Spain, there are not enough studies on it, therefore it would be of interest to carry out prospective studies, in order to confirm this increase in incidence.

[Shigellosis outbreak with 146 cases related to a fair]

BACKGROUND

On September 3, 2005, the Ciudad Real Public Health Service (Spain) received a report of 20 cases of gastroenteritis in the municipality of Daimiel. We conducted an investigation to determine the cause or causes of the outbreak and to implement control measures. Most of the cases involved young people who visited the municipality's fair.

METHODS

We carried out a descriptive study and an analytic case-control study. In the descriptive study, all variables of interest available in the medical records were included. In the case-control study, each case was matched with a control by age (plus or minus 5 years), gender, and attendance at the fair. Sixty-five cases and 65 controls were finally included in the study. Samples of foods and stools from food handlers were taken.

RESULTS

We found 196 cases, 146 of which were confirmed. The epidemic curve suggested a common source of infection with a short period of activity. The case-control study showed an association between infection and eating potatoes with a sauce at any of the fair's five food stalls (OR = 20.56; 95%CI, 6.15-75.93; p < 0.0001). Logistic regression analysis showed an association with eating potatoes in food stall number 2 (OR = 6.38; 95%CI, 1.70-23.90; p < 0.0059). Neither samples of foods nor stools from food handlers yielded any positive results. However, Shigella sonnei was isolated from stool samples from 20 cases.

CONCLUSIONS

The epidemiological study suggested that the most probable cause of the outbreak was a sauce, handmade with garlic, milk, and oil and served with the potatoes.

Climate change and heat-related mortality in six cities part 1: model construction and validation

Heat waves are expected to increase in frequency and magnitude with climate change. The first part of a study to produce projections of the effect of future climate change on heat-related mortality is presented. Separate city-specific empirical statistical models that quantify significant relationships between summer daily maximum temperature (T (max)) and daily heat-related deaths are constructed from historical data for six cities: Boston, Budapest, Dallas, Lisbon, London, and Sydney. 'Threshold temperatures' above which heat-related deaths begin to occur are identified. The results demonstrate significantly lower thresholds in 'cooler' cities exhibiting lower mean summer temperatures than in 'warmer' cities exhibiting higher mean summer temperatures. Analysis of individual 'heat waves' illustrates that a greater proportion of mortality is due to mortality displacement in cities with less sensitive temperature-mortality relationships than in those with more sensitive relationships, and that mortality displacement is no longer a feature more than 12 days after the end of the heat wave. Validation techniques through residual and correlation analyses of modelled and observed values and comparisons with other studies indicate that the observed temperature-mortality relationships are represented well by each of the models. The models can therefore be used with confidence to examine future heat-related deaths under various climate change scenarios for the respective cities (presented in Part 2).

Caracterización molecular de la cepa responsable de un brote de shigelosis en un centro escolar de Madrid

INTRODUCTION

The aim of this study is to describe a Shigella sonnei outbreak in a school.

METHOD

An epidemiological inquiry was performed. Stool samples from 5 patients were cultured. Molecular typing of the isolates was carried out by PFGE, MLST and plasmid analysis.

RESULTS

The attack rate was 14.3% (67 students). Shigella sonnei was isolated from all 5 patients. The four strains available for typing were indistinguishable.

CONCLUSION

These results suggest a common identity of the outbreak strain.