The epidemiology of infectious diseases and an outbreak in Queensland

Abstract

Epidemiological study (Chapter 2)

In Australia, influenza vaccination is recommended for all pregnant women. Evidence to date suggests influenza vaccination has not been associated with adverse birth outcomes, however there are still concerns about safety and risks of receiving a vaccine during pregnancy. This chapter describes a nested retrospective cohort study comprising 7,121 mother-infant pairs in Australia from 2012-2014. The study focussed on whether mothers who had received an influenza vaccination during pregnancy had poorer birth outcomes compared to unvaccinated women in pregnancy. Birth outcomes examined were infant birthweights and prematurity. I found there were no differences in birth outcomes between the vaccinated and unvaccinated groups. This was the first Australian study examining birth outcomes of influenza vaccination during pregnancy and as such, results will make an important contribution to the literature on this topic.

Analysis of a public health dataset (Chapter 3)

Morbidity and mortality of pertussis is highest in infants under six months of age. Control efforts focus on preventing disease in this age group by minimizing exposure by other infected cases. This project presents results from a retrospective case series analysis of all valid and probable pertussis notifications in Queensland from 1997-2014 by age group. Over this 18 year observation period, amongst children less than three years of age, notifications of pertussis were most common amongst infants <4 months of age. Increases in pertussis notifications from 2009 coincided with a substantial increase in the number of cases diagnosed by PCR. The results in this case series are consistent with that of overseas literature. It will important to monitor the outcomes of the implementation of the Queensland maternal pertussis vaccination program which commenced on 01 August 2014 regarding pertussis notifications in infants less than four months of age.

Outbreak investigation (Chapter 4)

This chapter describes an outbreak investigation of 85 confirmed cases of Salmonella Typhimurium (MLVA 03-12-11-12-524 and MLVA 03-13-11-12-524) in South-East Brisbane in January 2015. Cases experienced gastrointestinal illness following the consumption of Kim Bap (Korean style sushi). The descriptive study involved epidemiological, laboratory and environmental investigations. Twenty-two cases were hospitalised, seven of these (32%) were children. The likely vehicle of transmission of infection for this outbreak (Kim Bap sushi) was distributed by one producer to multiple food retail outlets in South-East Brisbane. Once supply of this product had ceased there were no further reported cases of illness. I was unable to determine any associations between food exposures and illness due to the absence of a comparison group.

Evaluation of a surveillance system (Chapter 5)

Hepatitis A virus (HAV) in Australia remains a nationally notifiable disease and control is considered to be a high public health priority. This evaluation of the current surveillance system for HAV in Queensland examined acceptability and timeliness. A detailed retrospective case series data analysis and genotype analysis was also conducted to determine sensitivity, representativeness and data quality. Age and sex data were complete, however risk factor data were largely incomplete. Data quality for travel history, post exposure prophylaxis vaccination, Indigenous status, mechanism of infection and hospitalisations were poor. Most cases of HAV are now acquired as a result of overseas travel or exposure to a returning overseas traveller. The timeliness of all aspects of the current system is reassuring however there needs to be a sustained improvement in completeness of data at every step, particularly for identification of Aboriginal and Torres Strait Islander people and for risk factor data. Show more