Polio in Sudan – high risk of international spread
2 March 2009 - The recent expansion of a prolonged outbreak of wild poliovirus type 1 (WPV1) in Sudan poses a very high risk of further international spread, requiring urgent and immediate outbreak response activities in the affected areas and heightened surveillance in countries at risk. Previously restricted to southern Sudan and western Ethiopia, the outbreak has now spread to Kenya, Uganda and northern Sudan (in Khartoum and Port Sudan).
Of particular concern is the confirmation of the WPV1 in Port Sudan. It is from this area that, from 2004 to 2006, WPV1 spread to re-infect several countries, including Saudi Arabia, Somalia, Yemen and Indonesia, causing outbreaks that resulted in more than 1,200 cases and over US$150 million in international emergency outbreak response costs. Due to the historical international spread of polioviruses from Port Sudan, the new international spread from southern Sudan to Kenya and Uganda, and the suboptimal quality of outbreak response activities in southern Sudan and western Ethiopia (monitoring data indicates that upwards of 30% of children remain un- or under-immunized with ≤3 doses of oral poliovirus vaccine), WHO assesses the risk of further international spread from the Sudan as very high.
Stopping this outbreak requires the full implementation of the international polio outbreak response standards, adopted by the World Health Assembly in May 2006, until transmission has been confirmed to be interrupted.
In northern Sudan, a large-scale supplementary immunization activity (SIA) began on 15 February with additional campaigns planned for 23 March and again in late-April. In southern Sudan, SIAs were held on 13 January and 23 February, with further activities planned for 23 March and late April, following which the onset of the rainy season in May could complicate the logistics of reaching all populations in this already difficult-to-access terrain. Consequently, particular attention is being given to closing the persistent OPV coverage gaps during the upcoming SIAs.
In coordination with the polio campaigns in the Sudan, plans for rapid outbreak response campaigns are being finalized for late March, late April and possibly again in late May in the affected areas of Kenya and Uganda. Genetic sequencing data suggests that the importations into these countries have been rapidly detected, improving the prospects for interrupting transmission in the near term if the campaigns are of sufficiently high quality to reach >90% of children in the affected areas.
It is important that countries across central Africa, the Horn of Africa and the Gulf strengthen surveillance for cases of acute flaccid paralysis (AFP), in order to rapidly detect any new poliovirus importations and facilitate a rapid response. Countries should also analyze routine immunization coverage data to identify any subnational gaps in population immunity to guide catch-up immunization activities and thereby minimize the consequences of any new virus introduction. Priority should be given to areas at high-risk of importations and where OPV3/DPT3 coverage is <80%.