Disease surveillance using a hidden Markov model.

BACKGROUND: Routine surveillance of disease notification data can enable the early detection of localised disease outbreaks. Although hidden Markov models (HMMs) have been recognised as an appropriate method to model disease surveillance data, they have been rarely applied in public health practice. We aimed to develop and evaluate a simple flexible HMM for disease surveillance which is suitable for use with sparse small area count data and requires little baseline data. METHODS: A Bayesian HMM was designed to monitor routinely collected notifiable disease data that are aggregated by residential postcode. Semi-synthetic data were used to evaluate the algorithm and compare outbreak detection performance with the established Early Aberration Reporting System (EARS) algorithms and a negative binomial cusum. RESULTS: Algorithm performance varied according to the desired false alarm rate for surveillance. At false alarm rates around 0.05, the cusum-based algorithms provided the best overall outbreak detection performance, having similar sensitivity to the HMMs and a shorter average time to detection. At false alarm rates around 0.01, the HMM algorithms provided the best overall outbreak detection performance, having higher sensitivity than the cusum-based Methods and a generally shorter time to detection for larger outbreaks. Overall, the 14-day HMM had a significantly greater area under the receiver operator characteristic curve than the EARS C3 and 7-day negative binomial cusum algorithms. CONCLUSION: Our findings suggest that the HMM provides an effective method for the surveillance of sparse small area notifiable disease data at low false alarm rates. Further investigations are required to evaluation algorithm performance across other diseases and surveillance contexts.

Applying cusum-based methods for the detection of outbreaks of Ross River virus disease in Western Australia.

BACKGROUND: The automated monitoring of routinely collected disease surveillance data has the potential to ensure that important changes in disease incidence are promptly recognised. However, few studies have established whether the signals produced by automated monitoring methods correspond with events considered by epidemiologists to be of public health importance. This study investigates the correspondence between retrospective epidemiological evaluation of notifications of Ross River virus (RRv) disease in Western Australia, and the signals produced by two cumulative sum (cusum)-based automated monitoring methods. METHODS: RRv disease case notification data between 1991 and 2004 were assessed retrospectively by two experienced epidemiologists, and the timing of identified outbreaks was compared with signals generated from two different types of cusum-based automated monitoring algorithms; the three Early Aberration Reporting System (EARS) cusum algorithms (C1, C2 and C3), and a negative binomial cusum. RESULTS: We found the negative binomial cusum to have a significantly greater area under the receiver operator characteristic curve when compared with the EARS algorithms, suggesting that the negative binomial cusum has a greater level of agreement with epidemiological opinion than the EARS algorithms with respect to the existence of outbreaks of RRv disease, particularly at low false alarm rates. However, the performance of individual EARS and negative binomial cusum algorithms were not significantly different when timeliness was also incorporated into the area under the curve analyses. CONCLUSION: Our retrospective analysis of historical data suggests that, compared with the EARS algorithms, the negative binomial cusum provides greater sensitivity for the detection of outbreaks of RRv disease at low false alarm levels, and decreased timeliness early in the outbreak period. Prospective studies are required to investigate the potential usefulness of these algorithms in practice.

Tackle the problem when it gets here: pandemic preparedness among small and medium businesses.

Globally, governments and health authorities are preparing for pandemic influenza and producing resources to promote preparedness planning; however, there is little information available to inform the design of strategies to promote preparedness. Three focus groups were conducted to identify and to describe beliefs and perceptions about pandemic influenza and response planning among small and medium business owners and managers. Most participants were not concerned about the risk of pandemic influenza, and none had engaged in any planning for a pandemic. Findings show that participants were uncertain of the modes of transmission of pandemic influenza and what precautions could be taken prior to, or in the event of, a pandemic. Among the most important findings was participants' perceived inability to effectively prevent or control the spread of influenza within their workplace. These findings have important implications for the design of communication strategies to promote preparedness.

Influenza pandemic preparedness: motivation for protection among small and medium businesses in Australia.

BACKGROUND: Community-wide preparedness for pandemic influenza is an issue that has featured prominently in the recent news media, and is currently a priority for health authorities in many countries. The small and medium business sector is a major provider of private sector employment in Australia, yet we have little information about the preparedness of this sector for pandemic influenza. This study aimed to investigate the association between individual perceptions and preparedness for pandemic influenza among small and medium business owners and managers. METHODS: Semi-structured face-to-face interviews were conducted with 201 small and medium business owners or managers in New South Wales and Western Australia. Eligible small or medium businesses were defined as those that had less than 200 employees. Binomial logistic regression analysis was used to identify the predictors of having considered the impact of, having a plan for, and needing help to prepare for pandemic influenza. RESULTS: Approximately 6 per cent of participants reported that their business had a plan for pandemic influenza, 39 per cent reported that they had not thought at all about the impact of pandemic influenza on their business, and over 60 per cent stated that they required help to prepare for a pandemic. Beliefs about the severity of pandemic influenza and the ability to respond were significant independent predictors of having a plan for pandemic influenza, and the perception of the risk of pandemic influenza was the most important predictor of both having considered the impact of, and needing help to prepare for a pandemic. CONCLUSION: Our findings suggest that small and medium businesses in Australia are not currently well prepared for pandemic influenza. We found that beliefs about the risk, severity, and the ability to respond effectively to the threat of pandemic influenza are important predictors of preparedness. Campaigns targeting small and medium businesses should emphasise the severity of the consequences to their businesses if a pandemic were to occur, and, at the same time, reassure them that there are effective strategies capable of being implemented by small and medium businesses to deal with a pandemic.

Timeliness of data sources used for influenza surveillance.

OBJECTIVE: In recent years, influenza surveillance data has expanded to include alternative sources such as emergency department data, absenteeism reports, pharmaceutical sales, website access and health advice calls. This study presents a review of alternative data sources for influenza surveillance, summarizes the time advantage or timeliness of each source relative to traditional reporting and discusses the strengths and weaknesses of competing approaches. METHODS: A literature search was conducted on Medline to identify relevant articles published after 1990. A total of 15 articles were obtained that reported the timeliness of an influenza surveillance system. Timeliness was described by peak comparison, aberration detection comparison and correlation. RESULTS: Overall, the data sources were highly correlated with traditional sources and had variable timeliness. Over-the-counter pharmaceutical sales, emergency visits, absenteeism and health calls appear to be more timely than physician diagnoses, sentinel influenza-like-illness surveillance and virological confirmation. CONCLUSIONS: The methods used to describe timeliness vary greatly between studies and hence no strong conclusions regarding the most timely source/s of data can be reached. Future studies should apply the aberration detection method to determine data source timeliness in preference to the peak comparison method and correlation.

Using GIS to create synthetic disease outbreaks.

BACKGROUND: The ability to detect disease outbreaks in their early stages is a key component of efficient disease control and prevention. With the increased availability of electronic health-care data and spatio-temporal analysis techniques, there is great potential to develop algorithms to enable more effective disease surveillance. However, to ensure that the algorithms are effective they need to be evaluated. The objective of this research was to develop a transparent user-friendly method to simulate spatial-temporal disease outbreak data for outbreak detection algorithm evaluation. A state-transition model which simulates disease outbreaks in daily time steps using specified disease-specific parameters was developed to model the spread of infectious diseases transmitted by person-to-person contact. The software was developed using the MapBasic programming language for the MapInfo Professional geographic information system environment. RESULTS: The simulation model developed is a generalised and flexible model which utilises the underlying distribution of the population and incorporates patterns of disease spread that can be customised to represent a range of infectious diseases and geographic locations. This model provides a means to explore the ability of outbreak detection algorithms to detect a variety of events across a large number of stochastic replications where the influence of uncertainty can be controlled. The software also allows historical data which is free from known outbreaks to be combined with simulated outbreak data to produce files for algorithm performance assessment. CONCLUSION: This simulation model provides a flexible method to generate data which may be useful for the evaluation and comparison of outbreak detection algorithm performance.

Pandemic influenza and critical infrastructure dependencies: possible impact on hospitals.

Hospitals will be particularly challenged when pandemic influenza spreads. Within the health sector in general, existing pandemic plans focus on health interventions to control outbreaks. The critical relationship between the health sector and other sectors is not well understood and addressed. Hospitals depend on critical infrastructure external to the organisation itself. Existing plans do not adequately consider the complexity and interdependency of systems upon which hospitals rely. The failure of one such system can trigger a failure of another, causing cascading breakdowns. Health is only one of the many systems that struggle at maximum capacity during "normal" times, as current business models operate with no or minimal "excess" staff and have become irreducible operations. This makes interconnected systems highly vulnerable to acute disruptions, such as a pandemic. Companies use continuity plans and highly regulated business continuity management to overcome process interruptions. This methodology can be applied to hospitals to minimise the impact of a pandemic.

"I have learnt ... a different way of looking at people's health": an evaluation of a prevocational medical training program in public health medicine and primary health care in remote Australia.

The purpose of this study was to gain insight into what prevocational medical practitioners (PMPs) learnt during a six-month public health medicine and primary health care training program (the Program) in remote Aboriginal Australia in 2001-2002. The Program's curriculum objectives included clinical and public health management of sexually transmitted infections, immunization, clinical audit and quality improvement, primary health care in remote Aboriginal communities, and working as part of an interdisciplinary team with health and non-health professionals, and lay people. The mode and location of delivery of these objectives was determined by the healthcare needs of the Kimberley population, and availability of safe, supported workplaces. Qualitative data from a variety of sources, including PMPs' reflective journals, were examined in the context of the Program's curriculum objectives and by conducting a content analysis of journal notes. Findings are presented using the curriculum objectives and other comments that emerged while examining the data. Preliminary data indicated that PMPs gained knowledge and practical experience in clinical and public health management of sexually transmitted infections, immunization and primary health care in poorly resourced remote Aboriginal settings. Deeper understandings of health and illness in a cross-cultural setting also developed, along with professional and personal growth, as illustrated by the following quotations from PMPs: "I have learnt ... a different way of looking at people's health ... I was encouraged to think more deeply than before about the whys and wherefores of medical practice, and thus consider the most effective ways of influencing patients' behaviours for the better." "I was encouraged to examine the thought processes behind the ways ... healthcare was provided ... [after leaving the Kimberley] I am constantly questioning the reason why we are practising medicine in a certain way in the big city hospitals-much to the consternation of my colleagues ... ." The Program was successful in teaching its first four PMPs the basic tools of public health medicine and remote area primary health care.

Approaches to the evaluation of outbreak detection methods.

BACKGROUND: An increasing number of methods are being developed for the early detection of infectious disease outbreaks which could be naturally occurring or as a result of bioterrorism; however, no standardised framework for examining the usefulness of various outbreak detection methods exists. To promote comparability between studies, it is essential that standardised methods are developed for the evaluation of outbreak detection methods. METHODS: This analysis aims to review approaches used to evaluate outbreak detection methods and provide a conceptual framework upon which recommendations for standardised evaluation methods can be based. We reviewed the recently published literature for reports which evaluated methods for the detection of infectious disease outbreaks in public health surveillance data. Evaluation methods identified in the recent literature were categorised according to the presence of common features to provide a conceptual basis within which to understand current approaches to evaluation. RESULTS: There was considerable variation in the approaches used for the evaluation of methods for the detection of outbreaks in public health surveillance data, and appeared to be no single approach of choice. Four main approaches were used to evaluate performance, and these were labelled the Descriptive, Derived, Epidemiological and Simulation approaches. Based on the approaches identified, we propose a basic framework for evaluation and recommend the use of multiple approaches to evaluation to enable a comprehensive and contextualised description of outbreak detection performance. CONCLUSION: The varied nature of performance evaluation demonstrated in this review supports the need for further development of evaluation methods to improve comparability between studies. Our findings indicate that no single approach can fulfil all evaluation requirements. We propose that the cornerstone approaches to evaluation identified provide key contributions to support internal and external validity and comparability of study findings, and suggest these be incorporated into future recommendations for performance assessment.

Reducing unmet needs: a prevocational medical training program in public health medicine and primary health care in remote Australia.

OBJECTIVES: To describe the development and implementation of a prevocational medical training program in public health medicine and primary health care in remote Australia and to evaluate the program's adherence to adult learning principles. METHODS: Reports, funding applications and other relevant material relating to the program were reviewed to document learning objectives, and teaching and program implementation strategies. RESULTS: The 24-week program employs two prevocational medical practitioners each year and comprises four weeks at Fremantle Hospital's sexual health clinic followed by 20 weeks in the Kimberley. Curriculum objectives include clinical and public health aspects of sexually transmitted infection management, immunisation, clinical audit and quality improvement, primary health care in remote Aboriginal communities, oral and written presentation skills and working as part of an interdisciplinary team. Teaching strategies used were in accordance with adult learning principles. CONCLUSIONS: Prevocational medical training in public health medicine and primary health care in remote Australia is achievable and reduces current gaps in prevocational medical education.

So far and yet so close: quality of management of diabetes in Australian and Canadian Indigenous communities.

OBJECTIVES: To compare quality of clinical management of Indigenous people with diabetes in remote areas of Australia and Canada. DESIGN: Clinical audit of diabetes management. SETTING: The Kimberley region of Western Australia and Northern Saskatchewan in Canada. SUBJECTS: One hundred and two Saskatchewan and 142 Kimberley patients from seven and 11 primary health services, respectively. MAIN OUTCOME MEASURES: Indicators of quality of diabetes clinical management during the preceding two years. RESULTS: Overall quality of management was poor. Retinopathy screening was better in the Kimberley than Saskatchewan (58% screened in the preceding two years cf 30%). Glycemic control of Saskatchewan patients was better than that of Kimberley patients (16% with optimal control vs. 9%). CONCLUSIONS: Continuing efforts at the level of health service organisation, patient and staff education, and creative ways to reduce barriers to access, as well as primary prevention initiatives, are required to counter the devastating effect of diabetes on Indigenous communities.

Quality of sexually transmitted infection clinical management and contact tracing outcomes in a remote area of high sexually transmitted infection endemicity.

OBJECTIVES: The objectives of this study were to assess health professionals' adherence to Western Australian sexually transmitted infection (STI) management guidelines and to document the outcomes of contact tracing in a remote Indigenous setting. METHODS: This article comprises 2 parts: a retrospective clinical audit of quality of clinical STI management and outcomes of contact tracing and an analysis of completeness of relevant laboratory investigations. RESULTS: Documented clinical STI management of index cases varied from 94% receiving treatment in accordance with the Guidelines, whereas only 48% underwent a clinical examination. Sexual contacts who underwent STI consultation had concordant (30%) and discordant (17%) STI(s). The proportion of patients with STI(s) in whom all appropriate laboratory investigations had been requested increased from 25% in 1998 to 9% to 49% in 2001-2002. CONCLUSIONS: This study demonstrates that quality of clinical STI management comparable to that observed overseas is possible despite the challenges of healthcare delivery in a remote setting.

Pathways to treatment for tuberculosis in Bali: patient perspectives.

The authors explored treatment-seeking behavior among people with tuberculosis (TB) in Bali, Indonesia. They conducted in-depth interviews with 5 people who had been diagnosed with TB and 6 people who were suspected of having TB but who had not yet received a diagnosis. Participants reported frequent delays in obtaining a diagnosis of TB and obtaining adequate treatment. The authors describe issues associated with treatment-seeking behavior using the following five main themes: awareness of TB-causes, symptoms, and seriousness; influence of others; treatment quality; treatment barriers and default; and stigma and fear. Their findings reinforce the importance of a comprehensive TB control program that provides quality diagnostic and treatment services, and patient and community education, and enables patient involvement in treatment.

Lack of SARS transmission among public hospital workers, Vietnam.

The severe acute respiratory syndrome (SARS) outbreak in Vietnam was amplified by nosocomial spread within hospital A, but no transmission was reported in hospital B, the second of two designated SARS hospitals. Our study documents lack of SARS-associated coronavirus transmission to hospital B workers, despite variable infection control measures and the use of personal protective equipment.

Patient views on the management of rheumatic fever and rheumatic heart disease in the Kimberley: a qualitative study.

OBJECTIVE: To describe, from a patient perspective, factors leading to suboptimal management of individuals with rheumatic fever (RF) and rheumatic heart disease (RHD) among members of the Kimberley population. METHOD: Qualitative in-depth semistructured and repeated interviews of seven Kimberley patients, or parents of children, with rheumatic fever and/or rheumatic heart disease, during 1998. RESULTS: Participants showed variable levels of understanding about RF/RHD, often relating to the need for secondary prophylaxis. Compliance with medication was closely linked with positive patient-staff interactions. From the perspective of health care, living in a remote location was frequently described as a negative influence. Participants desire more accessible and culturally appropriate opportunities for learning about their disease. CONCLUSIONS: Participants focused on issues closely related to effective and ineffective management of RF/RHD. The lessons learned are indicators for health staff attempting to improve the quality of management that people receive.

Screening for diabetic retinopathy in remote Australia: a program description and evaluation of a devolved model.

OBJECTIVES: To describe the diabetic retinopathy screening program operating in the Kimberley and evaluate recruitment into and the quality and timeliness of, the screening procedure. METHOD: Review of the documents relating to the Kimberley diabetic retinopathy screening program and analysis of Kimberley diabetic retinopathy screening database. RESULTS: The Kimberley Public Health Unit developed and maintains a program of training, credentialing and ongoing professional development for retinal camera practitioners and a Kimberley-wide database of retinal photographs taken for diabetic retinopathy screening. As a result of this program, diabetic retinopathy screening is available in or close to most diabetics' home towns/communities and 58% had undergone retinopathy screening in the preceding 2 years. Over 90% of sets of photographs were of excellent or adequate quality. There was a positive relationship between credentialing and photograph quality and timeliness of photographs being sent away for reporting. CONCLUSIONS: Quality diabetic retinopathy screening, at prevalences comparable to, or higher than, other urban and rural populations, can be achieved in a remote area.

Impact of lead transport on children's blood and environmental lead levels.

INTRODUCTION: A lead monitoring project was established in 1996 to monitor the environmental and health effects of lead being transported through a remote town in tarpaulin-covered trucks. METHODS: Dust samples from sites on the transport route were collected at 3-6 monthly intervals between 1996 and 1999. Annual blood lead testing clinics, offering voluntary testing to children, were conducted from 1997 to 1999. RESULTS: Of the 55 dust samples analysed, only nine contained particles of lead concentrate and these were present at very low levels. During the project 167 children were tested. The geometic mean of blood lead levels in 1997, 1998 and 1999 were 4.5 micro g/dL, 5.0 micro g/dL and 5.1 micro g/dL, respectively (all within the normal range). Residence on the transport route was not associated with higher lead levels (P > 0.05). CONCLUSIONS: Lead transport was not associated with any detectable environmental contamination or increase in children's blood lead levels.

A prospective study of infection and cardiovascular diseases: the Busselton Health Study.

BACKGROUND: Infectious agents might play a role in the aetiology of cardiovascular diseases. The aim was to determine the association of antibodies to implicated infectious agents with coronary heart disease (CHD) and stroke in a population-based prospective study. DESIGN: This study was based on a cohort of 1612 cardiovascular disease-free adults in the 1981 Busselton Health Survey. Primary risk factors were measured from stored serum and case-cohort sampling was used to reduce costs and preserve serum. The outcomes of interest were time to first CHD or stroke event. Serum antibody tests were carried out for all 218 CHD cases, all 119 stroke cases and a random subset of 451 subjects. METHODS: Sera were tested for antibodies to Chlamydia pneumoniae (IgG and IgA), and for IgG antibodies to Helicobacter pylori and cytomegalovirus (CMV). The association between serum antibody and risk of cardiovascular diseases was analysed using Cox proportional hazards regression. RESULTS: The estimated population prevalence was 24% for C. pneumoniae IgG, 7% for C. pneumoniae IgA, 58% for H. pylori and 85% had CMV antibody levels greater than 15 AU/mL. The estimated relative risk of CHD was around 1.2 for all antibodies examined, except for C. pneumoniae IgA for which it was less than one, and the estimated relative risk of stroke was around 0.85, however in all cases the 95% confidence interval included one. CONCLUSIONS: This study of an Australian population does not support an association between serum antibody levels to C. pneumoniae, H. pylori and CMV with development of cardiovascular diseases.

The quality of management of rheumatic fever/ heart disease in the Kimberley.

OBJECTIVE: To evaluate the quality of management of Kimberley patients with rheumatic fever (RF) and rheumatic heart disease (RHD). METHODS: A retrospective analysis of medical records for 215 residents of the Kimberley region of Western Australia, diagnosed with RF or RHD during the years 1982 to 1996. RESULTS: Among patients prescribed intramuscular penicillin for secondary prophylaxis, 67% of prescribed doses were given, with individuals receiving 8-100% of doses prescribed. Of patients recommended visiting specialist or echocardiographic review, 78% and 64% attended respectively. Only 34% of patients with RHD in 1996 were recommended dental review in 1996 or 1997. Appropriate blood testing occurred in 34% of the months in which people had anticoagulant prescribed. CONCLUSIONS: A clinical audit can be used to evaluate the management received by this population and hence identify areas to improve management. We found much room for improvement if optimal clinical outcomes are to be obtained.

Epizootic activity of Murray Valley encephalitis virus in an aboriginal community in the southeast Kimberley region of Western Australia: results of cross-sectional and longitudinal serologic studies.

Murray Valley encephalitis (MVE) virus is a mosquito-borne flavivirus causing severe encephalitis with a resultant high morbidity and mortality. In the period 1989-1993, we undertook a cross-sectional and longitudinal study by annually screening members of a small remote Aboriginal community in northwestern Australia for MVE virus antibodies. Of the estimated 250-300 people in the community, 249 were tested, and 52.6% had positive serology to MVE. The proportion testing positive increased with increasing age group, and males were slightly more likely to be positive than females. During the study period, a high proportion of the population seroconverted to MVE; the clinical/subclinical ratio seems to be lower than previously reported. Although MVE is mostly asymptomatic, the devastating consequences of clinical illness indicate that advice should be provided regarding the avoidance of mosquito bites. Our longitudinal study showed that the risk of seroconversion was similar for each age group, not just the young.