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)

European data sources for computing burden of (potential) vaccine-preventable diseases in ageing adults

BACKGROUND

To guide decision-making on immunisation programmes for ageing adults in Europe, one of the aims of the Vaccines and InfecTious diseases in the Ageing popuLation (IMI2-VITAL) project is to assess the burden of disease (BoD) of (potentially) vaccine-preventable diseases ((P)VPD). We aimed to identify the available data sources to calculate the BoD of (P)VPD in participating VITAL countries and to pinpoint data gaps. Based on epidemiological criteria and vaccine availability, we prioritized (P) VPD caused by Extra-intestinal pathogenic Escherichia coli (ExPEC), norovirus, respiratory syncytial virus, Staphylococcus aureus, and pneumococcal pneumonia.

METHODS

We conducted a survey on available data (e.g. incidence, mortality, disability-adjusted life years (DALY), quality-adjusted life years (QALY), sequelae, antimicrobial resistance (AMR), etc.) among national experts from European countries, and carried out five pathogen-specific literature reviews by searching MEDLINE for peer-reviewed publications published between 2009 and 2019.

RESULTS

Morbidity and mortality data were generally available for all five diseases, while summary BoD estimates were mostly lacking. Available data were not always stratified by age and risk group, which is especially important when calculating BoD for ageing adults. AMR data were available in several countries for S. aureus and ExPEC.

CONCLUSION

This study provides an exhaustive overview of the available data sources and data gaps for the estimation of BoD of five (P) VPD in ageing adults in the EU/EAA, which is useful to guide pathogen-specific BoD studies and contribute to calculation of (P)VPDs BoD.

Effect of Definitions of Acute Gastroenteritis Episodes Using Symptom Diaries in Paediatric Cohorts: A Systematic Review

Estimates of acute gastroenteritis (AGE) burden are difficult to compare between studies because of inconsistent definitions describing this illness. AGE definitions used in prospective, community-based childhood cohort studies were identified by searching databases for studies that collected daily observations of AGE symptoms. Disease definitions and refractory periods were extracted. Data from the Australian community-based Observational Research in Childhood Infectious Diseases birth cohort were used to calculate AGE incidence and duration using identified AGE definitions, and the World Health Organization definition for diarrhoea. Eight distinct AGE definitions were identified. All included loose stools and 7 included vomiting as symptoms. The refractory period separating episodes ranged from 1 to 21 days. When applied to the Observational Research in Childhood Infectious Diseases dataset, AGE incidence ranged from 0.8 to 2.6 episodes per child-year-at-risk, a 3-fold relative difference. Direct comparisons of rates from different cohorts can only be undertaken if a standard definition for AGE is adopted.

Factors that influence treatment-seeking expectations in response to infectious intestinal disease: Original survey and multinomial regression

BACKGROUND

Infectious intestinal disease affects 25% of the UK population annually; 1 in 50 affected people consult health professionals about their illness.

AIMS

We tested if anticipated treatment-seeking decisions for suspected infectious intestinal disease could be related to emotional response, tolerance of symptoms, or beliefs about the consequential benefits and harms of seeking treatment (or not).

METHODS

Questionnaire survey of adults living in the UK with statistical analysis of responses. A vignette was presented about a hypothetical gastrointestinal illness. People stated their emotional reactions, expected actions in response and beliefs about possible benefits or harms from seeking treatment (or not getting treatment). Multinomial regression looked for predictors of anticipated behaviour.

RESULTS

People were inclined to consult a GP when they believed that seeking treatment would be beneficial and that its absence would be harmful. Seeking treatment was less anticipated if the condition was expected to improve quickly. Respondents were also more likely to consult if they strongly disliked fever or headache, and/or if the illness made them feel anxious or angry. Treatment-seeking (or lack of it) was not linked to harms from treatment-seeking, other specific symptoms and emotional responses.

CONCLUSION

It was possible to link anticipated treatment-seeking behaviour to specific factors: expected prognosis, perceived benefits of seeking treatment, some emotions and some specific symptoms.

Prevalence and factors associated with infectious intestinal diseases in Ras Al Khaimah, United Arab Emirates, 2017: A population-based cross-sectional study

BACKGROUND

The United Arab Emirates (UAE) is a rapidly developing high-income country that has experienced significant population growth, urbanization, and improvements in the standard of living since its formation in 1971. Published estimates on the prevalence of infectious intestinal diseases (IID) in the UAE are scarce and exclusively based on hospital data. The aim of this study was to provide the first prevalence estimates of IID in the UAE.

METHODS

A population-based cross-sectional study design using a telephone-based questionnaire was used to estimate the IID prevalence in the previous 4 weeks in a representative sample of the Ras Al Khaimah (RAK) population from January to September 2017.

RESULTS

Data were collected from 1254 participants (57.3% male; 25.2% <18 years). The prevalence of IID was 4.2% in the 4 weeks prior to the interview. Multivariate logistic regression analysis identified that being female (odds ratio (OR) 2.4, 95% confidence interval (CI) 1.2-5.1) and having a middle-range monthly household income (approx. USD 4080-<6800: OR 5.42, 95% CI 1.15-25.48; approx. USD 6800-<9530: OR 7.13, 95% CI 1.47-34.57) were positively associated with IID. Age ≥6 years was negatively associated with IID (OR 0.95, 95% CI 0.90-0.99). Forty-nine percent of participants with an IID sought medical care and 20.8% took over-the-counter medication.

CONCLUSIONS

This study provides the first population-based prevalence estimates of IID in the UAE, which are similar to those reported in China (4%), but lower than those reported in Canada (10%), the Netherlands (7%), and the USA (6%).

Anatomy of a seasonal influenza epidemic forecast

Bayesian methods have been used to predict the timing of infectious disease epidemics in various settings and for many infectious diseases, including seasonal influenza. But integrating these techniques into public health practice remains an ongoing challenge, and requires close collaboration between modellers, epidemiologists, and public health staff. During the 2016 and 2017 Australian influenza seasons, weekly seasonal influenza forecasts were produced for cities in the three states with the largest populations: Victoria, New South Wales, and Queensland. Forecast results were presented to Health Department disease surveillance units in these jurisdictions, who provided feedback about the plausibility and public health utility of these predictions. In earlier studies we found that delays in reporting and processing of surveillance data substantially limited forecast performance, and that incorporating climatic effects on transmission improved forecast performance. In this study of the 2016 and 2017 seasons, we sought to refine the forecasting method to account for delays in receiving the data, and used meteorological data from past years to modulate the force of infection. We demonstrate how these refinements improved the forecast’s predictive capacity, and use the 2017 influenza season to highlight challenges in accounting for population and clinician behaviour changes in response to a severe season.

Social patterning of telephone health-advice for diarrhoea and vomiting: analysis of 24 million telehealth calls in England

OBJECTIVES

Gastrointestinal (GI) infections are common and most people do not see a physician. There is conflicting evidence of the impact of socioeconomic status (SES) on risk of GI infections. We assessed the relationship between SES and GI calls to two National Health Service (NHS) telephone advice services in England.

METHODS

Over 24 million calls to NHS Direct (2010-13) and NHS 111 (2013-15) were extracted from Public Health England (PHE) syndromic surveillance systems. The relationship between SES and GI calls was assessed using generalised linear models (GLM).

RESULTS

Adjusting for rurality and age-sex interactions, in NHS Direct, children in disadvantaged areas were at lower risk of GI calls; in NHS 111 there was a higher risk of GI calls in disadvantaged areas for all ages (0-4 years RR 1.27, 95% CI 1.25-1.29; 5-9 years RR 1.43, 95% CI 1.36-1.51; 10-14 years RR 1.36, 95% CI 1.26-1.41; 15-19 years RR 1.59, 95% CI 1.52-1.67; 20-59 years RR 1.50, 95% CI 1.47-1.53, 60 years and over RR 1.12, 95% CI 1.09-1.14).

CONCLUSIONS

Disadvantaged areas had higher risk of GI calls in NHS 111. This may relate to differences in exposure or vulnerability to GI infections, or propensity to call about GI infections.

Norovirus strain types found within the second infectious intestinal diseases (IID2) study an analysis of norovirus circulating in the community

BACKGROUND

Norovirus is the commonest cause of infectious intestinal disease (IID) worldwide. In the UK community incidence of norovirus has been estimated at 59/1000 population, equating to four million cases a year. Whilst norovirus infects people of all ages, a substantial burden occurs in infants and young children. The population of viruses found in sporadic cases among infants has been observed to be more diverse than that associated with outbreaks. In this study, we analysed norovirus-positive specimens collected during the second study of infectious intestinal diseases (IID2 Study) a national community cohort study conducted between April 2008 and August 2009 We examined the data for differences in circulating norovirus strains between two arms of a community cohort, and differences between genotypes and disease outcomes such as illness duration and symptom profiles.

METHODS

Analysis was conducted to assess genetic diversity of noroviruses in the community. We also assessed differences in the cycle threshold (Ct) value, as a proxy for viral load, between norovirus genogroups and genotypes, and differences in reported symptoms or length of illness in relation to genogroup and genotype.

RESULTS

There were 477 samples where norovirus was detected. Whilst 85% of people recovered within two days for vomiting; diarrhoea symptoms were reported to day 4 for 83% of the cases, and 10% of people reported symptoms of diarrhoea lasting between five and six days. Both diarrhoea and vomiting symptoms lasted longer in children aged < 5 years compared to adults. There was a significantly higher proportion of GII.4 in samples obtained from the GP arm of the study (chi-square = 17.8, p < 0.001) compared to samples received via post in the self-reporting arm. In the latter group, the prevalence of GII.6 was significantly higher (chi-square = 7.5, p < 0.001).

CONCLUSIONS

We found that there is a difference in disease severity by age group. Children aged < 5 years had longer duration of illness, with 10% still having diarrhoea at seven days, and vomiting of between four and five days. The duration of illness reported is higher overall than one might expect for cases in the community in otherwise healthy individuals which has implications for infection control. No differences were observed in relation to duration of vomiting and or diarrhoea by genotype.

A model for rapid, active surveillance for medically-attended acute gastroenteritis within an integrated health care delivery system

Background

This study presents a novel methodology for estimating all-age, population-based incidence rates of norovirus and other pathogens that contribute to acute gastroenteritis in the United States using an integrated healthcare delivery system as a surveillance platform.

Methods

All cases of medically attended acute gastroenteritis within the delivery system were identified from April 1, 2014 through September 30, 2016. A sample of these eligible patients were selected to participate in two phone-based surveys and to self-collect a stool sample for laboratory testing. To ascertain household transmission patterns, information on household members with acute gastroenteritis was gathered from participants, and symptomatic household members were contacted to participate in a survey and provide stool sample as well.

Results

54% of individuals who met enrollment criteria agreed to participate, and 76% of those individuals returned a stool sample. Among household members, 85% of eligible individuals agreed to participate, and 68% of those returned a stool sample. Participant demographics were similar to those of the eligible population, although minority racial/ethnic groups were somewhat underrepresented in the final sample.

Conclusions

This study demonstrates the feasibility of conducting acute infectious disease research within an integrated health care delivery system. The surveillance, sampling, recruitment, and data collection methods described here are broadly applicable to conduct baseline and epidemiological assessments, as well as for other research requiring representative samples of stool specimens.

A methodological framework for the evaluation of syndromic surveillance systems: a case study of England

BACKGROUND

Syndromic surveillance complements traditional public health surveillance by collecting and analysing health indicators in near real time. The rationale of syndromic surveillance is that it may detect health threats faster than traditional surveillance systems permitting more timely, and hence potentially more effective public health action. The effectiveness of syndromic surveillance largely relies on the methods used to detect aberrations. Very few studies have evaluated the performance of syndromic surveillance systems and consequently little is known about the types of events that such systems can and cannot detect.

METHODS

We introduce a framework for the evaluation of syndromic surveillance systems that can be used in any setting based upon the use of simulated scenarios. For a range of scenarios this allows the time and probability of detection to be determined and uncertainty is fully incorporated. In addition, we demonstrate how such a framework can model the benefits of increases in the number of centres reporting syndromic data and also determine the minimum size of outbreaks that can or cannot be detected. Here, we demonstrate its utility using simulations of national influenza outbreaks and localised outbreaks of cryptosporidiosis.

RESULTS

Influenza outbreaks are consistently detected with larger outbreaks being detected in a more timely manner. Small cryptosporidiosis outbreaks (<1000 symptomatic individuals) are unlikely to be detected. We also demonstrate the advantages of having multiple syndromic data streams (e.g. emergency attendance data, telephone helpline data, general practice consultation data) as different streams are able to detect different outbreak types with different efficacy (e.g. emergency attendance data are useful for the detection of pandemic influenza but not for outbreaks of cryptosporidiosis). We also highlight that for any one disease, the utility of data streams may vary geographically, and that the detection ability of syndromic surveillance varies seasonally (e.g. an influenza outbreak starting in July is detected sooner than one starting later in the year). We argue that our framework constitutes a useful tool for public health emergency preparedness in multiple settings.

CONCLUSIONS

The proposed framework allows the exhaustive evaluation of any syndromic surveillance system and constitutes a useful tool for emergency preparedness and response.

Norovirus transmission dynamics: a modelling review

Norovirus is one of the leading causes of viral gastroenteritis worldwide and responsible for substantial morbidity, mortality and healthcare costs. To further understanding of the epidemiology and control of norovirus, there has been much recent interest in describing the transmission dynamics of norovirus through mathematical models. In this study, we review the current modelling approaches for norovirus transmission. We examine the data and methods used to estimate these models that vary structurally and parametrically between different epidemiological contexts. Many of the existing studies at population level have focused on the same case notification dataset, whereas models from outbreak settings are highly specific and difficult to generalise. In this review, we explore the consistency in the description of norovirus transmission dynamics and the robustness of parameter estimates between studies. In particular, we find that there is considerable variability in estimates of key parameters such as the basic reproduction number, which may mean that the effort required to control norovirus at the population level may currently be underestimated.

An Ontology to Improve Transparency in Case Definition and Increase Case Finding of Infectious Intestinal Disease: Database Study in English General Practice

BACKGROUND

Infectious intestinal disease (IID) has considerable health impact; there are 2 billion cases worldwide resulting in 1 million deaths and 78.7 million disability-adjusted life years lost. Reported IID incidence rates vary and this is partly because terms such as "diarrheal disease" and "acute infectious gastroenteritis" are used interchangeably. Ontologies provide a method of transparently comparing case definitions and disease incidence rates.

OBJECTIVE

This study sought to show how differences in case definition in part account for variation in incidence estimates for IID and how an ontological approach provides greater transparency to IID case finding.

METHODS

We compared three IID case definitions: (1) Royal College of General Practitioners Research and Surveillance Centre (RCGP RSC) definition based on mapping to the Ninth International Classification of Disease (ICD-9), (2) newer ICD-10 definition, and (3) ontological case definition. We calculated incidence rates and examined the contribution of four supporting concepts related to IID: symptoms, investigations, process of care (eg, notification to public health authorities), and therapies. We created a formal ontology using ontology Web language.

RESULTS

The ontological approach identified 5712 more cases of IID than the ICD-10 definition and 4482 more than the RCGP RSC definition from an initial cohort of 1,120,490. Weekly incidence using the ontological definition was 17.93/100,000 (95% CI 15.63-20.41), whereas for the ICD-10 definition the rate was 8.13/100,000 (95% CI 6.70-9.87), and for the RSC definition the rate was 10.24/100,000 (95% CI 8.55-12.12). Codes from the four supporting concepts were generally consistent across our three IID case definitions: 37.38% (3905/10,448) (95% CI 36.16-38.5) for the ontological definition, 38.33% (2287/5966) (95% CI 36.79-39.93) for the RSC definition, and 40.82% (1933/4736) (95% CI 39.03-42.66) for the ICD-10 definition. The proportion of laboratory results associated with a positive test result was 19.68% (546/2775).

CONCLUSIONS

The standard RCGP RSC definition of IID, and its mapping to ICD-10, underestimates disease incidence. The ontological approach identified a larger proportion of new IID cases; the ontology divides contributory elements and enables transparency and comparison of rates. Results illustrate how improved diagnostic coding of IID combined with an ontological approach to case definition would provide a clearer picture of IID in the community, better inform GPs and public health services about circulating disease, and empower them to respond. We need to improve the Pathology Bounded Code List (PBCL) currently used by laboratories to electronically report results. Given advances in stool microbiology testing with a move to nonculture, PCR-based methods, the way microbiology results are reported and coded via PBCL needs to be reviewed and modernized.

Socioeconomic status is associated with symptom severity and sickness absence in people with infectious intestinal disease in the UK

BACKGROUND

The burden of infectious intestinal disease (IID) in the UK is substantial. Negative consequences including sickness absence are common, but little is known about the social patterning of these outcomes, or the extent to which they relate to disease severity.

METHODS

We performed a cross-sectional analysis using IID cases identified from a large population-based survey, to explore the association between socioeconomic status (SES) and symptom severity and sickness absence; and to assess the role of symptom severity on the relationship between SES and absence. Regression modelling was used to investigate these associations, whilst controlling for potential confounders such as age, sex and ethnicity.

RESULTS

Among 1164 cases, those of lower SES versus high had twice the odds of experiencing severe symptoms (OR 2.2, 95%CI;1.66-2.87). Lower SES was associated with higher odds of sickness absence (OR 1.8, 95%CI;1.26-2.69), however this association was attenuated after adjusting for symptom severity (OR 1.4, 95%CI;0.92-2.07).

CONCLUSIONS

In a large sample of IID cases, those of low SES versus high were more likely to report severe symptoms, and sickness absence; with greater severity largely explaining the higher absence. Public health interventions are needed to address the unequal consequences of IID identified.

Re-assessing the total burden of norovirus circulating in the United Kingdom population

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Norovirus is the commonest cause of GI disease in the UK.

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Less stringent diagnostic threshold Increases previous estimate by 26%.

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Re-assessed estimate equates to burden of infection at 59 per 1000 person years.

The second Infectious Intestinal Diseases study (IID2) estimated the incidence of norovirus in the UK at 47/1000 population (three million cases annually). Clinically significant norovirus was defined using a cycle threshold (ct) value of <30; a more stringent cut-off than used in diagnostic laboratories. The low infectious dose of norovirus means asymptomatic individuals potentially contribute to ongoing transmission. Using a less stringent but diagnostically relevant threshold increases the estimation of the population burden of norovirus infection by around 26% to 59/1000 person years (95% CI 52.32–64.98), equating to 3.7 million norovirus infections annually (3.3–4.1 million). With possible vaccines on the horizon for norovirus, having a good estimate of the total burden of norovirus infection, as well as symptomatic disease will be useful in helping to guide vaccination policy when candidate vaccines become available.

Model selection for seasonal influenza forecasting

Epidemics of seasonal influenza inflict a huge burden in temperate climes such as Melbourne (Australia) where there is also significant variability in their timing and magnitude. Particle filters combined with mechanistic transmission models for the spread of influenza have emerged as a popular method for forecasting the progression of these epidemics. Despite extensive research it is still unclear what the optimal models are for forecasting influenza, and how one even measures forecast performance.

In this paper, we present a likelihood-based method, akin to Bayes factors, for model selection when the aim is to select for predictive skill. Here, “predictive skill” is measured by the probability of the data after the forecasting date, conditional on the data from before the forecasting date. Using this method we choose an optimal model of influenza transmission to forecast the number of laboratory-confirmed cases of influenza in Melbourne in each of the 2010–15 epidemics. The basic transmission model considered has the susceptible-exposed-infectious-recovered structure with extensions allowing for the effects of absolute humidity and inhomogeneous mixing in the population. While neither of the extensions provides a significant improvement in fit to the data they do differ in terms of their predictive skill. Both measurements of absolute humidity and a sinusoidal approximation of those measurements are observed to increase the predictive skill of the forecasts, while allowing for inhomogeneous mixing reduces the skill.

We discuss how our work could be integrated into a forecasting system and how the model selection method could be used to evaluate forecasts when comparing to multiple surveillance systems providing disparate views of influenza activity.

Exploiting Bacterial Whole-Genome Sequencing Data for Evaluation of Diagnostic Assays: Campylobacter Species Identification as a Case Study

The application of whole-genome sequencing (WGS) to problems in clinical microbiology has had a major impact on the field. Clinical laboratories are now using WGS for pathogen identification, antimicrobial susceptibility testing, and epidemiological typing. WGS data also represent a valuable resource for the development and evaluation of molecular diagnostic assays, which continue to play an important role in clinical microbiology. To demonstrate this application of WGS, this study used publicly available genomic data to evaluate a duplex real-time PCR (RT-PCR) assay that targets mapA and ceuE for the detection of Campylobacter jejuni and Campylobacter coli, leading global causes of bacterial gastroenteritis. In silico analyses of mapA and ceuE primer and probe sequences from 1,713 genetically diverse C. jejuni and C. coli genomes, supported by RT-PCR testing, indicated that the assay was robust, with 1,707 (99.7%) isolates correctly identified. The high specificity of the mapA-ceuE assay was the result of interspecies diversity and intraspecies conservation of the target genes in C. jejuni and C. coli Rare instances of a lack of specificity among C. coli isolates were due to introgression in mapA or sequence diversity in ceuE The results of this study illustrate how WGS can be exploited to evaluate molecular diagnostic assays by using publicly available data, online databases, and open-source software.

Retrospective forecasting of the 2010–2014 Melbourne influenza seasons using multiple surveillance systems

Accurate forecasting of seasonal influenza epidemics is of great concern to healthcare providers in temperate climates, since these epidemics vary substantially in their size, timing and duration from year to year, making it a challenge to deliver timely and proportionate responses. Previous studies have shown that Bayesian estimation techniques can accurately predict when an influenza epidemic will peak many weeks in advance, and we have previously tailored these methods for metropolitan Melbourne (Australia) and Google Flu Trends data. Here we extend these methods to clinical observation and laboratory-confirmation data for Melbourne, on the grounds that these data sources provide more accurate characterizations of influenza activity. We show that from each of these data sources we can accurately predict the timing of the epidemic peak 4–6 weeks in advance. We also show that makingsimultaneoususe of multiple surveillance systems to improve forecast skill remains a fundamental challenge. Disparate systems provide complementary characterizations of disease activity, which may or may not be comparable, and it is unclear how a ‘ground truth’ for evaluating forecasts against these multiple characterizations might be defined. These findings are a significant step towards making optimal use of routine surveillance data for outbreak forecasting.

Modelling study to estimate the health burden of foodborne diseases: cases, general practice consultations and hospitalisations in the UK, 2009

OBJECTIVE

To generate estimates of the burden of UK-acquired foodborne disease accounting for uncertainty.

DESIGN

A modelling study combining data from national public health surveillance systems for laboratory-confirmed infectious intestinal disease (IID) and outbreaks of foodborne disease and 2 prospective, population-based studies of IID in the community. The underlying data sets covered the time period 1993-2008. We used Monte Carlo simulation and a Bayesian approach, using a systematic review to generate Bayesian priors. We calculated point estimates with 95% credible intervals (CrI).

SETTING

UK, 2009.

OUTCOME MEASURES

Pathogen-specific estimates of the number of cases, general practice (GP) consultations and hospitalisations for foodborne disease in the UK in 2009.

RESULTS

Bayesian approaches gave slightly more conservative estimates of overall health burden (∼511 000 cases vs 566 000 cases). Campylobacter is the most common foodborne pathogen, causing 280 400 (95% CrI 182 503-435 693) food-related cases and 38 860 (95% CrI 27 160-55 610) GP consultations annually. Despite this, there are only around 562 (95% CrI 189-1330) food-related hospital admissions due to Campylobacter, reflecting relatively low disease severity. Salmonella causes the largest number of hospitalisations, an estimated 2490 admissions (95% CrI 607-9631), closely followed by Escherichia coli O157 with 2233 admissions (95% CrI 170-32 159). Other common causes of foodborne disease include Clostridium perfringens, with an estimated 79 570 cases annually (95% CrI 30 700-211 298) and norovirus with 74 100 cases (95% CrI 61 150-89 660). Other viruses and protozoa ranked much lower as causes of foodborne disease.

CONCLUSIONS

The 3 models yielded similar estimates of the burden of foodborne illness in the UK and show that continued reductions in Campylobacter, Salmonella, E. coli O157, C. perfringens and norovirus are needed to mitigate the impact of foodborne disease.

Age-Specific Incidence Rates for Norovirus in the Community and Presenting to Primary Healthcare Facilities in the United Kingdom

In a prospective, population-based cohort study and a study of primary-healthcare consultations, we had a rare opportunity to estimate age-specific rates of norovirus-associated infectious intestinal disease in the United Kingdom. Rates in children aged <5 years were significantly higher than those for other age groups in the community (142.6 cases per 1000 person-years [95% confidence interval {CI}, 99.8-203.9] vs 37.6 [95% CI, 31.5-44.7]) and those for individuals presenting to primary healthcare (14.4 cases per 1000 person-years [95% CI, 8.5-24.5] vs 1.4 [95% CI, .9-2.0]). Robust incidence estimates are crucial for vaccination policy makers. This study emphasises the impact of norovirus-associated infectious intestinal disease, especially in children aged <5 years.

Early Detection of Epidemic GII-4 Norovirus Strains in UK and Malawi: Role of Surveillance of Sporadic Acute Gastroenteritis in Anticipating Global Epidemics

Noroviruses are endemic in the human population, and are recognised as a leading cause of acute gastroenteritis worldwide. Although they are a highly diverse group of viruses, genogroup-II genotype-4 (GII-4) noroviruses are the most frequently identified strains worldwide. The predominance of GII-4 norovirus strains is driven by the periodic emergence of antigenic variants capable of evading herd protection. The global molecular epidemiology of emerging GII-4 strains is largely based on data from outbreak surveillance programmes, but the epidemiology of GII-4 strains among sporadic or community cases is far less well studied. To understand the distribution of GII-4 norovirus strains associated with gastroenteritis in the wider population, we characterised the GII-4 norovirus strains detected during studies of sporadic cases of infectious gastroenteritis collected in the UK and Malawi between 1993 and 2009. Our data shows that GII-4 norovirus strains that have emerged as strains of global epidemic importance have circulated in the community up to 18 years before their recognition as pandemic strains associated with increases in outbreaks. These data may suggest that more comprehensive surveillance programmes that incorporate strains associated with sporadic cases may provide a way for early detection of emerging strains with pandemic potential. This may be of particular relevance as vaccines become available.

Estimating the Incidence of Acute Infectious Intestinal Disease in the Community in the UK: A Retrospective Telephone Survey

Objectives

To estimate the burden of intestinal infectious disease (IID) in the UK and determine whether disease burden estimations using a retrospective study design differ from those using a prospective study design.

Design/Setting

A retrospective telephone survey undertaken in each of the four countries comprising the United Kingdom. Participants were randomly asked about illness either in the past 7 or 28 days.

Participants

14,813 individuals for all of whom we had a legible recording of their agreement to participate

Outcomes

Self-reported IID, defined as loose stools or clinically significant vomiting lasting less than two weeks, in the absence of a known non-infectious cause.

Results

The rate of self-reported IID varied substantially depending on whether asked for illness in the previous 7 or 28 days. After standardising for age and sex, and adjusting for the number of interviews completed each month and the relative size of each UK country, the estimated rate of IID in the 7-day recall group was 1,530 cases per 1,000 person-years (95% CI: 1135–2113), while in the 28-day recall group it was 533 cases per 1,000 person-years (95% CI: 377–778). There was no significant variation in rates between the four countries. Rates in this study were also higher than in a related prospective study undertaken at the same time.

Conclusions

The estimated burden of disease from IID varied dramatically depending on study design. Retrospective studies of IID give higher estimates of disease burden than prospective studies. Of retrospective studies longer recall periods give lower estimated rates than studies with short recall periods. Caution needs to be exercised when comparing studies of self-reported IID as small changes in study design or case definition can markedly affect estimated rates.

Rapid Declines in Age Group-Specific Rotavirus Infection and Acute Gastroenteritis Among Vaccinated and Unvaccinated Individuals Within 1 Year of Rotavirus Vaccine Introduction in England and Wales

BACKGROUND

The oral infant rotavirus vaccine, Rotarix, was introduced in England and Wales in July 2013. We estimated the impact on laboratory-confirmed rotavirus infections and hospitalizations for all-cause acute gastroenteritis (AGE) during the first year after introduction.

METHODS

We extracted data on laboratory-confirmed rotavirus infections (July 2000 through June 2015) and all-cause AGE-associated hospitalizations (July 2007 through June 2014) for all age groups using national databases (LabBase2 and HES). We determined the ratio of the rate during the 2013-2014 rotavirus season to the rate during the prevaccination era.

RESULTS

In infants, there was a 77% decline (rate ratio [RR], 0.23; 95% confidence interval [CI], .16-.32) in laboratory-confirmed rotavirus infections and a 26% decline (RR, 0.74; 95% CI, .65-.84) in all-cause AGE-associated hospitalizations in 2013-2014, compared with the prevaccination era. Large reductions were also observed in older children, adults, and older adults. We estimated that 10 884 laboratory-confirmed infections and 50 427 all-cause AGE-associated hospital admissions were averted in 2013-2014. Similar reductions have been observed for laboratory-confirmed rotavirus infections during the 2014-2015 season.

CONCLUSIONS

The rapid declines in rotavirus infection and AGE in vaccinated and unvaccinated age groups within 1 year of introducing an infant rotavirus vaccination program are far greater than expected and than previously reported by other countries.

The incidence of acute gastrointestinal illness in Sweden

Aims: The aim of this study was to estimate the self-reported domestic incidence of acute gastrointestinal illness in the Swedish population irrespective of route of transmission or type of pathogen causing the disease. Previous studies in Sweden have primarily focused on incidence of acute gastrointestinal illness related to consumption of contaminated food and drinking water. Methods: In May 2009, we sent a questionnaire to 4000 randomly selected persons aged 0–85 years, asking about the number of episodes of stomach disease during the last 12 months. To validate the data on symptoms, we compared the study results with anonymous queries submitted to a Swedish medical website. Results: The response rate was 64%. We estimated that a total number of 2744,778 acute gastrointestinal illness episodes (95% confidence intervals 2475,641–3013,915) occurred between 1 May 2008 and 30 April 2009. Comparing the number of reported episodes with web queries indicated that the low number of episodes during the first 6 months was an effect of seasonality rather than recall bias. Further, the result of the recall bias analysis suggested that the survey captured approximately 65% of the true number of episodes among the respondents. Conclusions: The estimated number of Swedish acute gastrointestinal illness cases in this study is about five times higher than previous estimates. This study provides valuable information on the incidence of gastrointestinal symptoms in Sweden, irrespective of route of transmission, indicating a high burden of acute gastrointestinal illness, especially among children, and large societal costs, primarily due to production losses.

Building influenza surveillance pyramids in near real time, Australia

A timely measure of circulating influenza virus severity has been elusive. Flutracking, the Australian online influenza-like illness surveillance system, was used to construct a surveillance pyramid in near real time for 2011/2012 participants and demonstrated a striking difference between years. Such pyramids will facilitate rapid estimation of attack rates and disease severity.

Surveillance of diarrhoea in small animal practice through the Small Animal Veterinary Surveillance Network (SAVSNET)

Using the Small Animal Veterinary Surveillance Network (SAVSNET), a national small animal disease-surveillance scheme, information on gastrointestinal disease was collected for a total of 76 days between 10 May 2010 and 8 August 2011 from 16,223 consultations (including data from 9115 individual dogs and 3462 individual cats) from 42 premises belonging to 19 UK veterinary practices. During that period, 7% of dogs and 3% of cats presented with diarrhoea. Adult dogs had a higher proportional morbidity of diarrhoea (PMD) than adult cats (P <0.001). This difference was not observed in animals <1 year old. Younger animals in both species had higher PMDs than adult animals (P < 0.001). Neutering was associated with reduced PMD in young male dogs. In adult dogs, miniature Schnauzers had the highest PMD. Most animals with diarrhoea (51%) presented having been ill for 2-4 days, but a history of vomiting or haemorrhagic diarrhoea was associated with a shorter time to presentation. The most common treatments employed were dietary modification (66% of dogs; 63% of cats) and antibacterials (63% of dogs; 49% of cats). There was variability in PMD between different practices. The SAVNET methodology facilitates rapid collection of cross-sectional data regarding diarrhoea, a recognised sentinel for infectious disease, and characterises data that could benchmark clinical practice and support the development of evidence-based medicine.

Impact of the London 2012 Olympic and Paralympic Games on demand for microbiology gastrointestinal diagnostic services at the Public Health Laboratory London

Planning for the London 2012 Olympic and Paralympic Games at the Public Health Laboratory London was based on the requirement to meet potential increased demand with scalable capacity. The aim of this study was to determine the impact on demand for microbiology gastrointestinal diagnostic services during the Games period. Retrospective cross-sectional time-series data analysis was used to assess the number of gastrointestinal specimens received in the laboratory and the number of positive results. There was no increase in the number of gastrointestinal specimens received during the Games period, thus the Games had no impact on demand for microbiology gastrointestinal diagnostic services at the laboratory. There was a decrease in the number of public health specimens received for culture [incidence rate ratio = 0.34, 95% confidence interval (CI) = 0.13-0.86, P = 0.02] and a decrease in the number of culture positive community specimens (odds ratio = 0.59, 95 % CI = 0.40-0.85, P = 0.005), suggesting a decrease in gastrointestinal illness during the Games period. As previous planning assumptions were not based on actual specimen activity, the results of this study may modify the extent of additional planning for microbiological services required for mass gatherings.

Measuring underreporting and under-ascertainment in infectious disease datasets: a comparison of methods

BACKGROUND

Efficient and reliable surveillance and notification systems are vital for monitoring public health and disease outbreaks. However, most surveillance and notification systems are affected by a degree of underestimation (UE) and therefore uncertainty surrounds the 'true' incidence of disease affecting morbidity and mortality rates. Surveillance systems fail to capture cases at two distinct levels of the surveillance pyramid: from the community since not all cases seek healthcare (under-ascertainment), and at the healthcare-level, representing a failure to adequately report symptomatic cases that have sought medical advice (underreporting). There are several methods to estimate the extent of under-ascertainment and underreporting.

METHODS

Within the context of the ECDC-funded Burden of Communicable Diseases in Europe (BCoDE)-project, an extensive literature review was conducted to identify studies that estimate ascertainment or reporting rates for salmonellosis and campylobacteriosis in European Union Member States (MS) plus European Free Trade Area (EFTA) countries Iceland, Norway and Switzerland and four other OECD countries (USA, Canada, Australia and Japan). Multiplication factors (MFs), a measure of the magnitude of underestimation, were taken directly from the literature or derived (where the proportion of underestimated, under-ascertained, or underreported cases was known) and compared for the two pathogens.

RESULTS

MFs varied between and within diseases and countries, representing a need to carefully select the most appropriate MFs and methods for calculating them. The most appropriate MFs are often disease-, country-, age-, and sex-specific.

CONCLUSIONS

When routine data are used to make decisions on resource allocation or to estimate epidemiological parameters in populations, it becomes important to understand when, where and to what extent these data represent the true picture of disease, and in some instances (such as priority setting) it is necessary to adjust for underestimation. MFs can be used to adjust notification and surveillance data to provide more realistic estimates of incidence.

Investigating the link between the presence of enteroaggregative Escherichia coli and infectious intestinal disease in the United Kingdom, 1993 to 1996 and 2008 to 2009

There are an estimated 17 million human diarrhoea cases annually in the United Kingdom. In 2008 and 2009, enteroaggregative E. coli (EAEC) were identified in 1.9% of stools. However, it remains unclear whether there is a causal link between presence of EAEC and disease. This study used bacterial load, the presence of co-infections and demographic data to assess if EAEC was independently associated with intestinal infectious disease. Quantitative real-time PCR data (Ct values) generated directly from stool specimens for several pathogen targets were analysed to identify multiple pathogens, including EAEC, in the stools of cases and healthy controls. Sensitivity and specificity using Ct value (60% and 60%) was not useful for identifying cases or controls, but an independent association between disease and EAEC presence was demonstrated: multivariate logistic regression for EAEC presence (odds ratio: 2.41; 95% confidence interval: 1.78–3.26; p<0.001). The population-attributable fraction was 3.3%. The group of bacteria known as EAEC are associated with gastrointestinal disease in at least half of the cases with EAEC positive stools. We conclude that the current definition of EAEC, by plasmid gene detection, includes true pathogens as well as non-pathogenic variants.

The second study of infectious intestinal disease (IID2): increased rates of recurrent diarrhoea in individuals aged 65 years and above

Background

Infectious intestinal disease (IID) is a major health and economic burden in high-income countries. In the UK, there are an estimated 17 million IID cases annually, of which 6 million are caused by the 12 most common pathogens. Host factors that influence risk of IID are not well understood.

Methods

We analyzed data from the IID2 Study, a UK cohort that measured IID incidence, to investigate factors associated with recurrent IID. We calculated rates of IID by age group, sex, previous episodes experienced, and socioecomic indicators. We used Cox models to investigate factors associated with recurrent illness.

Results

The rate of IID was five times higher among infants than those aged 65 years and above (hazard ratio, HR = 5.0, 95% CI: 3.1 – 8.0). However, the association between previous IID and a subsequent IID episode was stronger in the elderly. Among those aged 65 years and above, each additional IID episode increased the rate of subsequent IID three-fold (HR = 3.1, 95% CI: 2.5 – 3.7). Among infants, the corresponding increase was 1.7-fold (HR = 1.7, 95% CI: 1.3 – 2.3).

Conclusions

Elderly populations have a high propensity for recurrent IID. More detailed studies are needed to identify vulnerable subgroups and susceptibility factors, and inform adequate control policies among the elderly.

Universal extraction method for gastrointestinal pathogens

A universal stool extraction method for recovery of nucleic acids (NAs) from gastrointestinal pathogens was developed to support rapid diagnostics for the London 2012 Olympics. The method involved mechanical disruption (bead beating) of the stools, followed by automated extraction and detection using real-time PCR. This method had been used extensively in the Second Infectious Intestinal Disease Study (IID2) for the isolation of NA from bacteria and parasites (and was effective for the robust recovery of Cryptosporidium spp.) but had not been used for enteric viruses. To ensure this method was universally suitable, panels of samples known to contain target bacteria, viruses or parasites were processed in triplicate using the pre-treatment method routinely used for each target and the new extraction method (bead beating). The extracts were tested using real-time PCR and the cycle threshold values were compared. The results from this study showed that bead beating improved yields for the bacterial and parasitic targets and was suitable for the viral targets. The implementation of this universal method should confer cost- and time-saving benefits and streamline the processes required for the characterization of an array of pathogens from faecal samples.

Assessing multiple foodborne, waterborne and environmental exposures of healthy people to potential enteric pathogen sources: effect of age, gender, season, and recall period

Information is lacking in Canada on the frequency of exposures of healthy people to enteric pathogen sources (i.e. water, food, animal contact) at the community level. This information is critical to develop more robust risk assessments and prioritize control measures. A 12-month-long cross-sectional telephone survey of 1200 healthy individuals in a sentinel community was performed. Survey respondents were divided into three recall period groups (3, 7, 14 days). The occurrence of 46 exposures (including water, animal contact, environmental contact and high-risk foods) was assessed per recall period. Effect of age, gender, and season on exposures was modelled and frequencies of exposure were extrapolated. Thirty-five exposures had similar occurrences across recall periods. Age was significant for 23 exposures, season for 18, and gender for three. Exposures that vary by age and season (i.e. bottled water, swimming, etc.) warrant consideration when investigating and analysing cases of enteric illness.

Acute gastrointestinal illness in adults in Germany: a population-based telephone survey

Population-based estimates of incidence and risk factors for acute gastrointestinal illness (AGI) are important for infectious disease surveillance and healthcare planning. We conducted a nationwide representative cross-sectional telephone survey of 21,262 adults over a 12-month period during 2008-2009 in Germany. Participants were asked if they had either AGI-related diarrhoea or vomiting in a 4-week recall period. We estimated 0·95 episodes/person per year (95% confidence interval 0·90-0·99), corresponding to 64·9 million episodes of AGI annually in adults, which results in 24·5 million outpatient visits, 19·9 million hospital days and 63·2 million days of work lost. We observed an overall declining trend of AGI with increasing age. Diarrhoea was more often reported than vomiting. The mean duration of illness was 3·8 days and did not differ between age groups. Social factors seemed to be weak predictors compared to state of health and health behaviour characteristics. This study allows international comparisons and contributes to the estimation of the global burden of AGI.

The burden of self-reported acute gastrointestinal illness in Italy: a retrospective survey, 2008-2009

A retrospective telephone survey (n = 3490) was conducted in Italy between 2008 and 2009 to estimate the occurrence of self-reported acute gastrointestinal illness (AGI) and to describe subjects' recourse to healthcare, using a symptom-based case definition. Three hundred and ten AGI cases were identified. The annual incidence rate was 1.08 episodes/person-year (95% confidence interval 0.90-1.14). The proportion of subjects consulting physicians was 39.5% while only 0.3% submitted a specimen for laboratory investigation. Risk factors for AGI and medical care-seeking were identified using logistic regression analysis. Females, children and young adults had a significantly higher incidence rate of AGI. Factors associated with medical care-seeking were age <10 years, presence of fever, diarrhoea, and duration of illness >3 days. Our results provide a relevant contribution towards estimating the global burden of AGI using standard methods that ensure a good level of comparability with other studies.

Longitudinal study of infectious intestinal disease in the UK (IID2 study): incidence in the community and presenting to general practice

OBJECTIVES

To estimate, overall and by organism, the incidence of infectious intestinal disease (IID) in the community, presenting to general practice (GP) and reported to national surveillance.

DESIGN

Prospective, community cohort study and prospective study of GP presentation conducted between April 2008 and August 2009.

SETTING

Eighty-eight GPs across the UK recruited from the Medical Research Council General Practice Research Framework and the Primary Care Research Networks.

PARTICIPANTS

6836 participants registered with the 88 participating practices in the community study; 991 patients with UK-acquired IID presenting to one of 37 practices taking part in the GP presentation study.

MAIN OUTCOME MEASURES

IID rates in the community, presenting to GP and reported to national surveillance, overall and by organism; annual IID cases and GP consultations by organism.

RESULTS

The overall rate of IID in the community was 274 cases per 1000 person-years (95% CI 254 to 296); the rate of GP consultations was 17.7 per 1000 person-years (95% CI 14.4 to 21.8). There were 147 community cases and 10 GP consultations for every case reported to national surveillance. Norovirus was the most common organism, with incidence rates of 47 community cases per 1000 person-years and 2.1 GP consultations per 1000 person-years. Campylobacter was the most common bacterial pathogen, with a rate of 9.3 cases per 1000 person-years in the community, and 1.3 GP consultations per 1000 person-years. We estimate that there are up to 17 million sporadic, community cases of IID and 1 million GP consultations annually in the UK. Of these, norovirus accounts for 3 million cases and 130,000 GP consultations, and Campylobacter is responsible for 500,000 cases and 80,000 GP consultations.

CONCLUSIONS

IID poses a substantial community and healthcare burden in the UK. Control efforts must focus particularly on reducing the burden due to Campylobacter and enteric viruses.

Incidence of self-reported acute gastrointestinal infections in the community in Poland: a population-based study

A retrospective cross-sectional survey of self-reported acute gastrointestinal infection (AGI) incidence in the community was performed in Poland, from December 2008 to November 2009. The aim of the study was to estimate the magnitude and distribution of self-reported AGI, in order to calibrate the routine AGI surveillance system in Poland. The study population were randomly selected residents of all Polish regions, having a fixed telephone line. An equal number of telephone interviews were collected each month, requesting the interviewee to identify gastrointestinal symptoms that had occurred in the previous 4 weeks. The international AGI case definition was used. In total 3583 complete interviews were obtained. The compliance ratio was 26%. Of 3583 respondents, 240 (6.7%) individuals fulfilled the AGI case definition. The annualized incidence of acute gastroenteritis was 0.9/person-year (95% confidence interval 0.8-1.0). Comparison of the obtained annual AGI estimate (33.3 million infections) with the number of cases reported to national surveillance during the corresponding period (73 512), yielded an underreporting factor of 453 cases occurring in the community for each reported case. Of the 240 AGI cases, 30.4% consulted a general practitioner, and 4.6% were admitted to hospital. Samples for microbiological confirmation were collected from four (1.6%) cases. This first population-based study in eastern Europe has confirmed that AGI places a high burden on Polish society, which is underestimated by national surveillance data. Efforts are necessary to improve AGI reporting and diagnostic practices in order to increase the effectiveness of the Polish surveillance system in detecting threats related to new AGI pathogens, new routes of transmission or the potential for international spread.

Burden of acute gastrointestinal illness in Denmark 2009: a population-based telephone survey

A cross-sectional telephone survey was conducted in Denmark throughout 2009 to determine the incidence of acute gastrointestinal illness (AGI). Using the Danish population register, a random population sample stratified by gender and age groups was selected and mobile or landline phone numbers found. Representative numbers of interviews were performed by gender, age group and month. A recently proposed international case definition of AGI, including cases with diarrhoea and/or vomiting in a 4-week recall period, was used. A total of 1853 individuals were included and 206 (11·1%) fulfilled the case definition; 78% reported diarrhoea. This corresponds to an overall standardized incidence rate of 1·4 (95% CI 1·2–1·6) episodes of AGI per person-year. The incidence rate was generally higher in the younger age groups; only being 2·3, 1·9 and 0·80 per person-year in the 0–9, 10–39 and ⩾40 years age groups, respectively. The incidence rate estimates were considerably higher when calculated from shorter recall periods.