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Michael Baker

Publications and source records attributed to Michael Baker.

At least 19 recordsLinked to original sources
PubMed2006

Key transmission parameters of an institutional outbreak during the 1918 influenza pandemic estimated by mathematical modelling.

AIM: To estimate the key transmission parameters associated with an outbreak of pandemic influenza in an institutional setting (New Zealand 1918). METHODS: Historical morbidity and mortality data were obtained from the report of the medical officer for a large military camp. A susceptible-exposed-infectious-recovered epidemiological model was solved numerically to find a range of best-fit estimates for key epidemic parameters and an incidence curve. Mortality data were subsequently modelled by performing a convolution of incidence distribution with a best-fit incidence-mortality lag distribution. RESULTS: Basic reproduction number (R0) values for three possible scenarios ranged between 1.3, and 3.1, and corresponding average latent period and infectious period estimates ranged between 0.7 and 1.3 days, and 0.2 and 0.3 days respectively. The mean and median best-estimate incidence-mortality lag periods were 6.9 and 6.6 days respectively. This delay is consistent with secondary bacterial pneumonia being a relatively important cause of death in this predominantly young male population. CONCLUSION: These R0 estimates are broadly consistent with others made for the 1918 influenza pandemic and are not particularly large relative to some other infectious diseases. This finding suggests that if a novel influenza strain of similar virulence emerged then it could potentially be controlled through the prompt use of major public health measures.

Adult↗
PubMed2006

Why the tuberculosis incidence rate is not falling in New Zealand.

AIMS: To assess the role of migration from high-incidence countries, HIV/AIDS infection, and prevalence of multi-drug resistant organisms as contributors to tuberculosis (TB) incidence in New Zealand (NZ) relative to ongoing local transmission and reactivation of disease. METHODS: TB notification data and laboratory data for the period 1995 to 2004 and population data from the 1996 and 2001 Census were used to calculate incidence rates of TB by age and ethnicity, country of birth (distinguishing high and low -incidence countries), and interval between migration and onset of disease. Published reports of multi-drug-resistant TB for the period 1995 to 2004 were reviewed. Anonymous HIV surveillance data held by AIDS Epidemiology Group were matched with coded and anonymised TB surveillance data to measure the extent of HIV/AIDS coinfection in notified TB cases. RESULTS: Migration of people from high-TB incidence countries is the main source of TB in NZ. Of those who develop TB, a quarter does so within a year of migration, and a quarter of this group (mainly refugees) probably enter the country with pre-existing disease. Rates of local TB transmission and reactivation of old disease are declining steadily for NZ-born populations, except for NZ-born Maori and Pacific people under 40. HIV/AIDS and multi-drug-resistant organisms are not significant contributors to TB incidence in NZ and there is no indication that their role is increasing. CONCLUSION: TB incidence is not decreasing in NZ mainly due to migration of TB infected people from high-incidence countries and subsequent development of active disease in some of them in NZ. This finding emphasises the importance of regional and global TB control initiatives. Refugees and migrants are not acting as an important source of TB for most NZ-born populations. Those caring for them should have a high level of clinical suspicion for TB.

Acquired Immunodeficiency Syndrome↗
PubMed2006

Tuberculosis epidemiology in New Zealand: 1995-2004.

AIMS: To describe the epidemiology of tuberculosis (TB) in New Zealand (NZ) for the 10-year period 1995-2004, and to place this in the context of long-term incidence trends. METHODS: We calculated TB incidence rates since the early 1920s using published data. A more detailed analysis examined TB notification and laboratory data for the period 1995 to 2004 using population denominator data from the 1996 and 2001 Census. We calculated incidence rates by age, sex, ethnicity, place of residence, country of birth, and deprivation for the two 5-year periods: 1995 to 1999 and 2000 to 2004. We also calculated and compared TB case fatality and mortality rates for those periods. We described outbreaks by using TB outbreak reporting data. RESULTS: The long-term decline in TB incidence in NZ halted in the mid-1980s, and in the last two decades, annual rates have stabilised at around 10 cases per 100,000. The average rate for 1995-2004 period was 10.3 per 100,000. The TB incidence rate in NZ is higher than that in Australia, USA, and Canada, and slightly lower than that in the UK. Within NZ there are marked ethnic differences in rates, with age-standardised incidence rates 10.5, 22.3, and 36.5 times higher in Maori, Pacific peoples, and people of Other ethnicity respectively than the rate in Europeans. Rates generally increase with age. Approximately two-thirds (64.6%) of people with TB were born overseas. TB case fatality and mortality rates in NZ are declining and are comparable to those in Australia, Canada, USA, and the UK. Twenty-four TB outbreaks, including 221 cases, were reported between mid-1996 and 2004. CONCLUSIONS: TB is not declining in NZ. The burden of disease is very unevenly distributed across the population with marked ethnic inequalities.

Adolescent↗
PubMed2006

Regulation of chicken contamination is urgently needed to control New Zealand's serious campylobacteriosis epidemic.

New Zealand's campylobacteriosis epidemic reached a new peak in May 2006 with the annualised national notification rate exceeding 400 per 100,000 for the first time, the highest national rate reported in the literature. The epidemic is estimated to cause at least 1 fatality a year, >800 hospitalisations, and >100,000 cases in the community, and cost the New Zealand economy 75 million dollars per annum. There is overwhelming epidemiological and laboratory evidence that fresh chicken is the dominant source of human infection. The seriousness of this epidemic justifies rapid, decisive action to reduce human exposure to this pathogen. There is good international evidence to support removal of fresh chicken from the food supply, with its reintroduction only when it can be shown to pose a very low risk to human health. Because freezing can substantially reduce Campylobacter levels, frozen chicken could be substituted to allow continued consumption of this popular food. Efforts to reduce Campylobacter colonisation of poultry flocks and contamination during chicken processing and distribution, along with continued consumer education, are important, but do not appear sufficient to control this epidemic in the short to medium term.

Animals↗
PubMed2006

Blinded evaluation of the effects of high definition and magnification on perceived image quality in laryngeal imaging.

OBJECTIVES: Advances in commercial video technology have improved office-based laryngeal imaging. This study investigates the perceived image quality of a true high-definition (HD) video camera and the effect of magnification on laryngeal videostroboscopy. METHODS: We performed a prospective, dual-armed, single-blinded analysis of a standard laryngeal videostroboscopic examination comparing 3 separate add-on camera systems: a 1-chip charge-coupled device (CCD) camera, a 3-chip CCD camera, and a true 720p (progressive scan) HD camera. Displayed images were controlled for magnification and image size (20-inch [50-cm] display, red-green-blue, and S-video cable for 1-chip and 3-chip cameras; digital visual interface cable and HD monitor for HD camera). Ten blinded observers were then asked to rate the following 5 items on a 0-to-100 visual analog scale: resolution, color, ability to see vocal fold vibration, sense of depth perception, and clarity of blood vessels. Eight unblinded observers were then asked to rate the difference in perceived resolution and clarity of laryngeal examination images when displayed on a 10-inch (25-cm) monitor versus a 42-inch (105-cm) monitor. A visual analog scale was used. These monitors were controlled for actual resolution capacity. RESULTS: For each item evaluated, randomized block design analysis demonstrated that the 3-chip camera scored significantly better than the 1-chip camera (p < .05). For the categories of color and blood vessel discrimination, the 3-chip camera scored significantly better than the HD camera (p < .05). For magnification alone, observers rated the 42-inch monitor statistically better than the 10-inch monitor. CONCLUSIONS: The expense of new medical technology must be judged against its added value. This study suggests that HD laryngeal imaging may not add significant value over currently available video systems, in perceived image quality, when a small monitor is used. Although differences in clarity between standard and HD cameras may not be readily apparent on small displays, a large display size coupled with HD technology may impart improved diagnosis of subtle vocal fold lesions and vibratory anomalies.

Equipment Design↗
PubMed2006

The business case for patient safety.

The leadership team at University Health Network describes why it decided to pursue a new information technology initiative to substantially reduce human and system errors and omissions associated with medication management.

Humans↗
PubMed2006

Internalization of near-infrared fluorescent dyes within isolated leukocyte populations.

Scientists have expressed continued interest in the development of microsensor technology that can indicate toxicity that occurs within a cell after a chemical challenge. One of the more useful approaches of microsensor technology is the application of fluorescent spectroscopy to indicate early-stage injury with optimal specificity and decreased background interference. If the toxicity is detected during the early onset period of injury, then the probability for therapeutic recovery is promising. There has been increasing interest in the use of infrared (IR) and near infrared (NIR) dyes as biological microsensors due to their fluorescent spectral characteristics. Three of the most essential characteristics are the ability to minimize background interference by extraneous biological matrices, to exhibit optimal molar absorptivity and quantum yields, to maintain chronic cellular homeostasis. Therefore, the present study was developed to determine if selected NIR dyes would distribute within isolated neutrophil populations without altering normal cellular homeostasis using fluorescent wavelength analysis. The results demonstrate that selected NIR dyes undergo internalization within target cell populations while maintaining cell viability and homeostasis. In addition, these dyes demonstrate changes in absorbance and fluorescence analysis after the immune cells were challenged with a stimulant. Moreover, critical cellular functions, such as degranulation and superoxide production were not compromised by the internalization of the NIR dyes. These data suggest that selected NIR dyes can undergo intracellular uptake within neutrophil cultures without altering the normal functional capabilities of the targeted cell population.

Animals↗
PubMed2006

Implementation of a computerized physician order entry system of medications at the University Health Network--physicians' perspectives on the critical issues.

There are many reasons why most hospitals have not adopted physician order entry systems for medications. It is a costly endeavour (Kuperman and Gibson 2003) that can cause major disruptions to workflow for physicians, pharmacists and nurses. Yet, the technology can reduce medication errors, especially with sophisticated decision support. We have presented many of the lessons learned from our successful implementation experience. To date, over 90% of medication orders are entered by physicians. The technology must be ready for the implementation. System issues such as errors, slowness and freezing give ready opportunity for critics who will claim the system is just not ready for real-time. Through rigorous testing, we were able to avoid issues previously seen in our pilot study. Usability testing with end-users was also critical in both guiding decision-making as well as validating that the system was ready for implementation. Proper training and support were also necessary. To ensure ready adoption, decision support was optimized to reduce the volume of less important alerts. Most importantly, we found that active physician involvement at multiple levels was key. This ensured that physicians understood from a high-level perspective that this change was necessary. Planning for specific implementation details had the benefit of input from physicians working in the area. Day-to-day issues of our residents and staff were also addressed promptly.

Attitude of Health Personnel↗
PubMed2005

Prevalence and risk factors for Chlamydia trachomatis infection in female New Zealand university students.

AIMS: To measure the prevalence of urogenital Chlamydia trachomatis infection in a sample of sexually active female university students, to identify risk factors associated with infection, and to measure the uptake of screening. METHODS: Female students aged 18-25 years, presenting to a university student health service from March to October 2003, were invited to participate. Information on demographic details and sexual behaviour was collected with a self-completed questionnaire. The students were tested for Chlamydia infection using the Roche Amplicor CT/NG PCR test of first void urine specimens. RESULTS: Chlamydia prevalence was 2.7% (19/715). Infection was associated with previous sexually transmitted infection (STI), non-European ethnicity, and irregular use of condoms. Most participants were not using condoms regularly despite the risk of STI. Screening was technically straightforward and the participation rate was 59.9% (718/1199). CONCLUSIONS: New Zealand needs to develop and implement an adequately resourced and evidence-based Chlamydia control strategy. This strategy should contain national guidelines on screening in a range of settings, including universities, as well as strategies for primary prevention of Chlamydia and other STI. Clinicians treating university-aged students should consider opportunistic Chlamydia screening for all of those who are sexually active. Further research, preferably in conjunction with intervention studies, is essential to assess the prevalence of Chlamydia in other populations.

Adolescent↗
PubMed2005

The potential impact of the next influenza pandemic on a national primary care medical workforce.

BACKGROUND: Another influenza pandemic is all but inevitable. We estimated its potential impact on the primary care medical workforce in New Zealand, so that planning could mitigate the disruption from the pandemic and similar challenges. METHODS: The model in the "FluAid" software (Centers for Disease Control and Prevention, CDC, Atlanta) was applied to the New Zealand primary care medical workforce (i.e., general practitioners). RESULTS: At its peak (week 4) the pandemic would lead to 1.2% to 2.7% loss of medical work time, using conservative baseline assumptions. Most workdays (88%) would be lost due to illness, followed by hospitalisation (8%), and then premature death (4%). Inputs for a "more severe" scenario included greater health effects and time spent caring for sick relatives. For this scenario, 9% of medical workdays would be lost in the peak week, and 3% over a more compressed six-week period of the first pandemic wave. As with the base case, most (64%) of lost workdays would be due to illness, followed by caring for others (31%), hospitalisation (4%), and then premature death (1%). CONCLUSION: Preparedness planning for future influenza pandemics must consider the impact on this medical workforce and incorporate strategies to minimise this impact, including infection control measures, well-designed protocols, and improved health sector surge capacity.

Journal Article↗
PubMed2005

Pathogenic accumulation of APP in fast twitch muscle of IBM patients and a transgenic model.

Inclusion body myositis (IBM) is the most common age-related degenerative skeletal muscle disorder. The aberrant intracellular accumulation of the beta-amyloid (Abeta) peptide within skeletal muscle is a pathological hallmark of IBM. Skeletal muscle is comprised of both slow and fast twitch fibers, which are present in different proportions in various muscles. It remains unclear if fast and/or slow twitch fibers are differentially involved in IBM pathogenesis. To better understand the molecular pathogenesis of IBM, we analyzed human IBM muscle biopsies and muscle from a transgenic mouse model of IBM (MCK-betaAPP). Here we report that the majority of histopathologically-affected fibers in human IBM biopsies were type II fast fibers. Skeletal muscle from MCK-betaAPP mice exhibited higher transgene expression and steady-state levels of human betaAPP in fast type IIB fibers compared to slow type I fibers. These findings indicate that fast twitch fibers may selectively accumulate and be more vulnerable to betaAPP- and Abeta-mediated damage in IBM. These findings also highlight parallels between the MCK-betaAPP mice and the human IBM condition.

Aged↗
PubMed2004

A descriptive epidemiology of giardiasis in New Zealand and gaps in surveillance data.

INTRODUCTION: Giardia is the most commonly notified waterborne disease in New Zealand, which has high incidence rates compared with other developed countries. Four years of giardiasis notification data were analysed to describe the epidemiological patterns of infection in New Zealand and compared with local and international data. METHODS: Anonymised information was collected nationally for 7818 notified cases of giardiasis between July 1996 and June 2000. International data were collected from the data sources of respective countries. Infection rates adjusted for confounding factors were calculated and presented by age, gender, ethnicity, and area using statistical and spatial methods. RESULTS: Most cases occurred in the 1-4 year age group followed by the 25-44 year age group, and were of Pakeha/European ethnicity. Ethnicity was unknown for 18% of cases, thus affecting demographic calculations. Rates were elevated for several Health Districts in New Zealand (West Coast, Wellington, Waikato, Auckland, Hawke's Bay, Hutt, Rotorua, and Tauranga). CONCLUSIONS: The higher rates of giardiasis observed in New Zealand, in comparison with other developed countries, may be related to environmental or social factors. Time-trend analysis suggests a seasonal pattern. This study identified vulnerable groups and major data-gaps. Recommendations for improvements in disease surveillance and data quality are discussed. Geographical information system (GIS) applications are useful for disease monitoring.

Adolescent↗