WHO has published Poliovirus in South Sudan and Madagascar. Excerpt:
In separate and unrelated events, circulating vaccine-derived polioviruses (cVDPVs) have been confirmed in South Sudan and Madagascar.
In South Sudan, 2 cases due to cVDPV type 2 (cVDPV2) have been confirmed. The strains were isolated from 2 acute flaccid paralysis (AFP) cases in Unity state, with onset of paralysis on 9 September and 12 September 2014, respectively. In Unity state, as many as 33% of children remain under-immunized against poliovirus. Both cases are from an internally-displaced persons camp in Unity state. Unity state has been affected by civil unrest, leading to population displacements and declining vaccination coverage in most of the areas.
In 2014, South Sudan has been participating in regional Horn of Africa outbreak response, given the risk posed by an ongoing wild poliovirus type 1 (WPV1) outbreak affecting the region (with cases in 2014 in parts of Somalia and Ethiopia).
Two National Immunization Days (NIDs) were conducted in April (with trivalent oral polio vaccine – OPV) and May (with bivalent OPV). In response to confirmation of the cVDPV2, NIDs were held on 4 November with trivalent OPV and further Subnational Immunization Days (SNID) covering the 3 states with civil unrest (Unity, Upper Nile and Jonglei) are planned for 2 December 2014 and January 2015 with trivalent OPV.
The objective is to rapidly stop the cVDPV2 in the internally-displaced persons camp and prevent further spread, while further boosting immunity to type 1 polio and minimize risk of re-infection from other parts of the Horn of Africa.
In Madagascar, cVDPV type 1 (cVDPV1) has been confirmed after the virus was isolated from 1 case of AFP (onset of paralysis on 29 September 2014) and 3 healthy contacts. The most recent supplementary immunization activities in Madagascar were conducted in December 2011/January 2012.
SNIDs are planned for December, with NIDs to be held in January 2015. An estimated more than 25% of children remain under-immunized against poliovirus in the country. Madagascar was previously affected by a cVDPV2 outbreak in 2001/2002 (resulting in 5 cases) and in 2005 (resulting in 5 cases). A VDPV was also isolated during a research study among healthy children in Toliara I in 2011.
Concerted outbreak response each time rapidly stopped those events. However, repeated emergence of separate cVDPV events underscores the risk of these events occurring in populations which are not fully immunized and of the importance of maintaining high levels of vaccination coverage.