Evaluating the acute flaccid paralysis surveillance system in South Africa, 2005-2009 - an analysis of secondary data

INTRODUCTION: Acute Flaccid Paralysis (AFP) surveillance was adopted by World Health Organization (WHO) to monitor progress towards poliomyelitis eradication. South Africa Department of Health (DoH) routinely collects AFP surveillance data but has no documented evidence of its epidemiological use. The study discusses the epidemiology of AFP in South Africa from 2005-9, evaluates performance of the AFP surveillance system, and identifies components that require strengthening. METHODS: A retrospective descriptive analysis was conducted on secondary AFP surveillance data for South Africa for the period 2005-2009, consisting of all children. RESULTS: South Africa reported 1501 AFP cases between 2005 and 2009. Of these, 67.2% were <5years of age, and 54.3% were male. None of the cases were confirmed poliomyelitis, and ten (0.7%) were classified as polio-compatible. The national annualized non-polio AFP detection rate increased from 1.6 in 2005 to 2.1 non-polio AFP cases/100,000 children <15years in 2008-9. All performance indicators met the WHO-specified targets except two. Between 2007 and 2009, 51.5%, 55.3% and 65% of specimens, respectively, reached the laboratory within 72hours of being sent (WHO target is ≥80%). Proportion of stool specimens where non-polio enterovirus was isolated decreased from 22.5% in 2006 to <1% in 2008 and 2009 (WHO target is ≥10%). CONCLUSION: The AFP surveillance system met most WHO-specified epidemiological and laboratory performance standards. The surveillance programme needs to address problems of delayed specimen arrival to the laboratory and incomplete documentation of laboratory findings in the national AFP surveillance database.