The Clinical Epidemiology of Childhood Encephalitis in Australia

Encephalitis is a complex neurological syndrome caused by inflammation of the brain that occurs most commonly in children. There are limited contemporary data regarding the incidence, causes and outcome of childhood encephalitis from Australia. In these doctoral studies I aimed to address these important knowledge gaps regarding the clinical epidemiology of childhood encephalitis. Firstly, after an extensive review of the literature, I identified a lack of contemporary recommendations for the diagnosis and management of encephalitis in children and adults in Australia. In response, I led the development and publication of consensus clinical guidelines for Australia and New Zealand (Britton et al. Internal Medicine Journal 2015). Secondly, having identified that the burden of childhood encephalitis was poorly defined in Australia, I analysed national datasets to retrospectively determine the incidence and causes of both childhood hospitalisations and deaths attributed to encephalitis in Australia (Britton et al. Archives of Disease in Childhood 2016). The average annual hospitalisation rate of childhood encephalitis from 2000 to 2012 was 3.8 per 100 000 population ≤14 years (95% CI 3.6 to 4.0), with a statistically significant decline across the study period. Vaccination has contributed to this decline and altered the aetiological spectrum with reductions in measles (including SSPE), mumps, and VZV encephalitis. Other key findings were that age was an important determinant of hospitalisation rate, mortality rate, and cause and that a high proportion of childhood encephalitis cases (up to 59%) did not have a specified cause. The average annual childhood encephalitis mortality rate was 2.4 per 1,000,000 population ≤14 years (95%CI 2.1-2.7) over a 26 year period (1979-2004), and declined significantly influenced by reductions in deaths due to measles (including SSPE), and HSV. I also determined a rise in the overall proportion of encephalitis deaths with ‘unspecified’ aetiology. Thirdly, given limitations of these administrative datasets in determining the causes, frequency and outcome of childhood encephalitis, I was involved in the design of and led implementation of the Australian Childhood Encephalitis (ACE) study, a prospective cohort study based on active, enhanced hospital surveillance, to rigorously determine the causes and consequences of childhood encephalitis in Australia