'Silent' and 'noisy' areas: acute flaccid paralysis surveillance at subnational level, Australia, 2001-2015.

Background: Acute flaccid paralysis (AFP) surveillance rates are used as an indicator of surveillance sensitivity to detect poliomyelitis with an expected rate of ≥1 case per 100 000 population in children under 15 years of age.

Methods: The Australian AFP detection rates at sub-national (statistical local area) level were analysed using χ2 goodness of fit tests and exact Poisson probabilities for the combined years 2001-2015 to detect 'silent areas', which may require improved AFP detection efforts, and areas with greater than expected rates, which may indicate unexplained clusters such as those due to enterovirus infection.

Results: Eight (n=8/87, 9%) local areas had AFP surveillance detection rates that were less than expected, and eighteen local areas (n=18/87, 21%) had rates that were greater than expected. However, based on available evidence, it is unlikely that these indicated previously unidentified, enterovirus clusters.

Conclusions: While Australia has regularly met the national AFP surveillance performance indicators, at the subnational level nine per cent of local areas demonstrated statistically significant lower AFP detection rates. All countries, even those with relatively small populations, should actively identify silent AFP areas to prompt surveillance improvements.