'Foul air, foul water, impure food, and unwholesome dwellings': Health Protection in New South Wales

Abstract

This thesis presents the results of research projects I completed to fulfil the requirements of the Masters of Philosophy (Applied Epidemiology) at the Australian National University. I completed these projects while based at Health Protection NSW, across the Environmental Health and Communicable Diseases Branches. In June 2018, a cluster of febrile illnesses was identified among raspberry workers from a farm on the mid-north coast of NSW. Initial testing did not identify a cause, but eventually leptospirosis was detected via PCR. We conducted an investigation to identify the outbreak source and risk factors for infection, to guide prevention and control measures. We detected cases through a range of surveillance measures and developed case definitions. We conducted a case-control study among raspberry workers on the farm, to ascertain risk factors, and conducted environmental investigations. We identified 84 cases over a 5-month period, making it the largest known outbreak of leptospirosis in Australia. Our case-control study provided evidence that workers were likely exposed through scratches inflicted during harvesting, which we think became contaminated with environmental leptospires from mice. Our findings helped to guide control measures, including enhanced glove use, doxycycline prophylaxis and rodent control. I conducted two projects on Legionnaires' disease. I reviewed the epidemiology of Legionnaires' disease in NSW between 2001 and 2018. While Legionnaires' disease remains relatively rare, notification rates have increased. However it is unclear how much this may be due to increased testing versus a true increase in disease. This review also highlighted that changes to the recording of data in the notification database could improve the ability to monitor the epidemiology of disease. This helped inform an aspect of my next project, for which I conducted an evaluation of the NSW legionellosis surveillance system, in terms of both the infectious diseases and environmental health components. I conducted stakeholders interviews, reviewed documents, and participated in aspects of surveillance, including several cluster investigations and made recommendations on areas for improvements in the system. Key recommendations included to: develop the informatics systems to make routinely collected surveillance data more useful and accessible when needed; use centralised mapping of case exposures routinely; develop standard operating procedures to make clear the steps that should be taken in response to a case or outbreak, and the parties responsible; and strengthen the links between the communicable diseases and environmental health components of the system. I conducted a linked data study on influenza, using linked notification and hospital admission data. I used this data to determine the number and proportion of influenza notifications that are admitted each year, including to intensive care. These measures are useful in providing an enhanced picture of influenza severity. In particular, the proportion of admitted influenza patients requiring admission to intensive care can be used as an indicator of the seriousness of influenza relatively unaffected by testing rates. The measures established in this study may be useful to assess and report as measures of the severity of influenza during and at the end of annual influenza seasons. In addition to these core projects, I contributed to a range of other work, including outbreak investigations, responding to a health risk assessment of contaminated land, conducting audits of emergency department management of influenza patients and anti-viral stock, investigating and responding to a cluster of mushroom poisoning, organising a workshop on multi-drug resistant gonococcal infection, as well as teaching, conference attendance and presentations. Through completing these projects, I was able to make valuable contribution to knowledge in this field and to protecting public health.