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Open Access Research article

An evaluation of the sensitivity of acute flaccid paralysis surveillance for poliovirus infection in Australia

Rochelle E Watkins1*, P Anthony J Martin2, Heath Kelly3, Ben Madin4 and Charles Watson1

Author Affiliations

1 Australian Biosecurity CRC for Emerging Infectious Disease, Faculty of Health Sciences, Curtin University of Technology, Perth, Australia

2 Department of Agriculture and Food, Bunbury, Australia

3 Victorian Infectious Diseases Reference Laboratory, North Melbourne, Australia

4 AusVet Animal Health Services, Broome, Australia

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BMC Infectious Diseases 2009, 9:162  doi:10.1186/1471-2334-9-162

Published: 30 September 2009

Abstract

Background

World Health Organization (WHO) targets for acute flaccid paralysis (AFP) surveillance, including the notification of a minimum rate of AFP among children, are used to assess the adequacy of AFP surveillance for the detection of poliovirus infection. Sensitive surveillance for poliovirus infection in both developed and developing countries is essential to support global disease eradication efforts. We applied recently developed methods for the quantitative evaluation of disease surveillance systems to evaluate the sensitivity of AFP surveillance for poliovirus infection in Australia.

Methods

A scenario tree model which accounted for administrative region, age, population immunity, the likelihood of AFP, and the probability of notification and stool sampling was used to assess the sensitivity of AFP surveillance for wild poliovirus infection among children aged less than 15 years in Australia. The analysis was based on historical surveillance data collected between 2000 and 2005. We used a surveillance time period of one month, and evaluated the ability of the surveillance system to detect poliovirus infection at a prevalence of 1 case per 100 000 persons and 1 case per million persons.

Results

There was considerable variation in the sensitivity of AFP surveillance for poliovirus infection among Australian States and Territories. The estimated median sensitivity of AFP surveillance in Australia among children aged less than 15 years was 8.2% per month at a prevalence of 1 case per 100,000 population, and 0.9% per month at a prevalence of 1 case per million population. The probability that Australia is free from poliovirus infection given negative surveillance findings following 5 years of continuous surveillance was 96.9% at a prevalence of 1 case per 100,000 persons and 56.5% at a prevalence of 1 case per million persons.

Conclusion

Given the ongoing risk of poliovirus importation prior to global eradication, long term surveillance is required to provide a high degree of confidence in freedom from poliovirus infection in Australia, particularly if a low prevalence of infection is assumed. Adherence to the WHO surveillance targets would considerably improve the sensitivity of surveillance for poliovirus infection in Australia.