Applied Epidemiology in Victoria
Date
2016
Authors
Cutcher, Zoe
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Abstract
The Health Protection Branch of the Victorian Government
Department of Health and Human Services monitors and responds to
incidents that could adversely affect the health of Victorians.
During 2014-2015, I completed a field placement with the branch,
assisting with numerous public health investigations and
responses. In doing so I fulfilled the requirements of the Master
of Philosophy in Applied Epidemiology (MAE). The skills I gained
are demonstrated in this thesis.
Evaluation of a public health surveillance system is a core
requirement for the MAE program. I evaluated Victoria’s
surveillance and response to legionellosis, which includes both
disease surveillance and environmental surveillance and response
arms. I found little evidence to support the current practice of
sampling and disinfecting cooling towers around the home and
workplace for sporadic cases. Improved co-ordination between
databases and strategic use of spatial software could help
develop more targeted and useful approaches in the future.
I embarked on two epidemiological projects. I designed a cross
sectional study examining the prevalence of Legionella in
domestic potable water and developed participant resources
including letters to explain results, meeting the MAE requirement
to communicate findings to a non-scientific audience. The study
was not completed due to legal considerations; however the
proposal and relevant participant resources are included as an
appendix.
I completed an epidemiological project estimating the number of
notified sporadic Salmonella Typhimurium 9 Phage type 9 cases
likely to be associated with a recurrent outbreak source during a
five year period. I examined 301 clinical Salmonella isolates,
including sporadic and outbreak isolates from a series of linked
outbreaks, and used multi-locus variable number tandem repeat
analysis and whole genome sequence results to estimate the number
of isolates genetically linked to the outbreak strain. Outbreak
cases accounted for just one third of all isolates estimated to
be closely related to the main outbreak clade. This project
inspired my lesson from the field, in which I taught MAE
colleagues how to analyse MLVA data.
I investigated an outbreak of Salmonella Typhimurium phage type
44 at a school function. I conducted a cohort study and
interviewed twenty-nine out of thirty guests, of which ten were
affected. Roast beef appetiser was the most likely food vehicle
for Salmonella infection. Cross-contamination from raw eggs
during preparation was a possible source.
I analysed a public health dataset to assist a public health
investigation into suspected antimony exposure in a rural mining
town in Victoria. Residents were concerned about potential health
effects from exposure to antimony dust from a local mine. Many
sought urinary antimony testing to quantify exposure, with
numerous elevated results. I used multivariate regression to
examine risk factors for elevated urinary antimony and
demonstrated residential proximity to the mine was not associated
with urinary antimony results. Overwhelmingly, the largest risk
factor for elevated results was the month of testing, consistent
with false positive laboratory reports.
This thesis documents my experience and capabilities gained
during the MAE program, and demonstrates my contribution to
protecting the public health of Victorians.
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Keywords
Epidemiology, Infectious disease, Applied epidemiology, Legionella, Legionnaire's Disease, Outbreak, Outbreak Investigation, Whole genome sequencing, Genomics, Public health surveillance, Disease surveillance, Masters of Applied Epidemiology
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