Aileen J. Plant

A review of Q fever in Australia 1991-1994

Abstract: Q fever continues to be an important disease in Australia. Despite the development of an effective vaccine that has been commercially available since 1989, the number of cases notified has continued to increase. This study reviewed national notifications of Q fever between 1991 and 1994, togetherwith demographic, socioeconomic and occupational information, to investigate temporal and spatial disease patterns. Based on notification data, Q fever can be considered primarily a disease of adult males that occurs in eastern Australia: southern Queensland and northern New South Wales have the highest levels of activity. A significant association between Q fever activity of areas and the presence of livestock was found. A strong association with the meat industry was also confirmed. Q fever is conservatively estimated to cost Australia around A

Incidence and prevalence of hepatitis C among clients of a Brisbane methadone clinic: factors influencing hepatitis C serostatus

1 million and more than 1700 weeks of work time annually. There is a need to increase awareness of this disease and its prevention. An extension program in rural communities and provision of vaccine to all abattoir workers would appear to be sensible public health approaches

Lack of association between seropositivity to Chlamydia pneumoniae and carotid atherosclerosis

Abstract: The objective of this study was to describe the incidence and prevalence of hepatitis C infection among clients of a methadone program in Queensland. The clinical notes of clients receiving methadone for treatment of opiate dependence who first registered at the clinic after 1989 were perused for information about their serological status for hepatitis C and hepatitis B infections during a six–week period in 1994. We followed hepatitis C negative clients until August–September 1995. At study entry, 69 per cent of the clients were recorded as being hepatitis C positive. Of those who were negative, the seroconversion rate was 11 per 100 person–years. The high incidence and prevalence of hepatitis C among methadone clients emphasises the need for effective early intervention strategies to prevent the transmission of hepatitis C among injecting drug users.

Does smoking explain sex differences in the global tuberculosis epidemic

Since the Chlamydia pneumoniae (C. pneumoniae)-specific antibody was shown to be associated with acute myocardial infarction and chronic coronary heart disease, the role of C. pneumoniae in the etiology of cardiovascular disease has been studied by a number of groups. We investigated the association between the C. pneumoniae-specific antibody, measured by microimmunofluorescence, risk factors for cardiovascular disease, and atherosclerosis in a randomly selected urban population. Overall, immunoglobulin-G (IgG) seroprevalence to C. pneumoniae in this sample of 1,034 subjects was 58%, whereas IgA seroprevalence was 32%. There was a decline in seropositivity with age for IgG but not IgA. Men were more likely than women to be IgG (66% vs 51%, chi-square p = 0.001) and IgA seropositive (36% vs 28%, chi-square p = 0.005). Current smokers had higher IgA seropositivity than nonsmokers (43% vs 30%). Those patients with a family history of cerebrovascular disease were more likely to have IgG antibody than those without (75% vs 57%, chi-square p= 0.007). Neither IgG nor IgA seropositivity was associated with the standard risk factors of hypertension, hyperlipidemia, or family history of ischemic heart disease, nor was seropositivity associated with carotid intima medial thickening (IMT) or atherosclerotic plaque as measured by carotid B-mode ultrasound. There was no difference between those participants who were IgG or IgA seropositive and seronegative in measurements of mean IMT, prevalence of abnormal IMT, and percentage with atherosclerotic plaque. In conclusion, although C. pneumoniae was associated with several risk factors for cardiovascular disease in a large cross-sectional population, we found no independent association between seroprevalence to C. pneumoniae and carotid atherosclerosis as measured by carotid IMT.

Timeliness of Data Sources Used for Influenza Surveillance

To date there has been no satisfactory explanation of the worldwide excess of tuberculosis (TB) notifications among adult males. We investigated the epidemiological basis for sex differences in TB notifications in high-burden countries using available group-level data. Multiple linear regression analysis was used to explore the ecological relationship between smoking and sex differences in TB notifications among high-burden countries. Cigarette consumption was a significant predictor of the sex ratio of TB notifications, and explained 33% of the variance in the sex ratio of TB notifications. Our findings suggest that smoking is an important modifiable factor which has a significant impact on the global epidemiology of TB, and emphasize the importance of tobacco control in countries with a high incidence of TB. This analysis provides support for the interpretation of sex differences in worldwide TB notification rates as indicative of true differences in the epidemiology of TB between males and females.

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

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.

Disease surveillance using a hidden Markov model

BackgroundThe 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.MethodsRRv 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.ResultsWe 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.ConclusionOur 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.

Pathways to Treatment for Tuberculosis in Bali: Patient Perspectives:

BackgroundRoutine 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.MethodsA 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.ResultsAlgorithm 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.ConclusionOur 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.

Clinical Description of a Completed Outbreak of SARS in Vietnam, February-May 2003

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.

Predictors of tuberculin reactivity among prospective Vietnamese migrants: the effect of smoking

We investigated the clinical manifestations and course of all probable severe acute respiratory syndrome (SARS) patients in the Vietnam outbreak. Probable SARS cases were defined by using the revised World Health Organization criteria. We systematically reviewed medical records and undertook descriptive statistical analyses. All 62 patients were hospitalized. On admission, the most prominent symptoms were malaise (82.3%) and fever (79.0%). Cough, chest pain, and shortness of breath were present in approximately one quarter of the patients; 79.0% had lymphopenia; 40.3% had thrombocytopenia; 19.4% had leukopenia; and 75.8% showed changes on chest radiograph. Fever developed on the first day of illness onset, and both respiratory symptoms and radiographic changes occurred on day 4. On average, maximal radiographic changes were observed on day 10, and fevers subsided by day 13. Symptoms on admission were nonspecific, although fever, malaise, and lymphopenia were common. The complications of SARS included invasive intubation and ventilation (11.3%) and death (9.7%).