The Clinical Epidemiology of Acute Flaccid Paralysis in Australian Children

Abstract

Acute flaccid paralysis (AFP) surveillance is a key component of the continuing global effort to eradicate poliovirus. In Australia, it is carried out by the Australian Paediatric Surveillance Unit and the Paediatric Active Enhanced Disease Surveillance Network (PAEDS). In 25 years, no polio has been detected, however AFP surveillance has also captured data on a variety of conditions causing non-polio AFP, including paralytic disease due to increasingly recognised non-polio enteroviruses (NPEV). This thesis identified the lack of contemporary data on the clinical epidemiology of non-polio AFP affecting Australian children, addressing this with a retrospective review of PAEDS surveillance data over ten years, 2007-2017. Of 400 cases non-polio AFP captured, 50.7% were male; 45% of cases were children aged 0-4 years, 7.3% were aged <1 year. Estimated annual incidence of AFP was 1.9 cases per 100,000 children aged <15 years. Lower limb paralysis was the most frequent presenting symptom. The most frequent diagnoses were Guillain-Barre syndrome (33.8%), acute disseminated encephalo-myelitis (18.3%) and transverse myelitis (17.3%). No secular trend was seen across all AFP cases nor amongst in the three major diagnoses. Periods of increased case frequency were however observed across all three major diagnoses in 2013 and 2016, aligning with detection of cases of non-polio anterior horn cell disease and increased detection of NPEV from cases in the same time-period. Further analysis of the 2016 cluster demonstrated a previously undetected cluster of acute flaccid myelitis (AFM), a newly-recognised entity with specific radiological features on MRI imaging and established links to NPEV overseas. The findings in this thesis has led to updated surveillance practices to better recognise AFM, and promotes the importance of expanded organism testing in all cases of AFP to better detect and describe the impact of NPEV in Australia.