Acute Flaccid Paralysis in Australian Children from 2007 to 2017: clinical spectrum and epidemiology.

INTRODUCTION: Acute flaccid paralysis (AFP) surveillance continues globally as part of the World Health Organization's goal to eradicate poliomyelitis. The Australian Paediatric Surveillance Unit (APSU), Paediatric Active Enhanced Disease Surveillance (PAEDS) network, and National Enterovirus Reference Laboratory (NERL) collaborate in acute flaccid paralysis surveillance in Australia, capturing and reviewing cases of AFP for all etiologies in order to exclude poliovirus. . We aimed to describe the AFP epidemiology in childhood over an eleven year period.

METHODS: Data were reported nationally by paediatricians via prospective APSU surveillance, PAEDS surveillance nurses at five tertiary paediatric hospitals and NERL from 2007 to 2017. Children aged 0-15 years with AFP were included. We combined APSU, PAEDS and NERL datasets, analysed epidemiological trends and described clinical features and investigations for major diagnoses.

RESULTS: Of 590 AFP-compatible cases, 49% were male; 47% were aged 0-4 years, 9% aged <1 year.. Annual incidence of AFP was 1.3 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 (GBS; 36%), transverse myelitis (TM; 17%) and acute disseminated encephalomyelitis (ADEM; 15%). No secular trend was seen in frequency of AFP cases nor amongst major diagnoses. Seasonality was observed with ADEM occurring more frequently in winter. We observed periods of increased AFP frequency in 2013 and 2016, coinciding with increased reporting of non-polio anterior horn cell disease (AHCD) and detection of non-polio enterovirus (NPEV).

CONCLUSIONS: Estimated incidence of GBS, ADEM and TM in Australian children were comparable with international rates. There was stable incidence of AFP in Australian children between 2007 and 2017. GBS, ADEM and TM are the major causes of AFP. We observed clustering of cases associated with NPEV that emphasises a need for ongoing vigilance in surveillance given continue emerging infectious disease threats.