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WHO EMRO Weekly Epidemiological Monitor: Volume 16; Issue no 01; 01 January 2023

Detection of cVDPV2 in Sudan

On 18 December 2022, the Federal Ministry of Health, Sudan notified WHO of the detection of circulating vaccine-derived poliovirus type 2 (cVDPV2) in a child with acute flaccid paralysis (AFP) from West Darfur, Western Sudan. A field investigation was conducted and a risk assessment is currently ongoing by local and national public health authorities, supported by partners of the Global Polio Eradication Initiative, and an outbreak response has been initiated.

Editorial Note

Wild poliovirus is the most commonly known form of poliovirus. However, circulating vaccinederived poliovirus or cVDPV is another form of polio that can spread within communities. While cVDPVs are rare, they have been increasing in recent years due to low immunization rates within communities. cVDPV type 2 (cVDPV2) is the most prevalent, with 428 cases occurring globally in 2022.
In recent years cVDPV2 cases have increased across the Eastern Mediterranean Region.
People’s movements across borders underscore the risk of importation across and beyond the Region (See map). The cVDPV2 cases count in 2022 was 164 cases (1 from Sudan, 4 from Somalia and 159 from Yemen).
In Sudan, the last reported outbreak was declared in 2020. It caused paralysis in 58 children in 15 out of 18 states. The outbreak was caused by a cVDPV2 imported from Chad. This strain has been detected in 8 neighbouring countries before and after Sudan’s outbreak.
Sudanese health authorities and partners responded to the outbreak through implementing a robust outbreak response plan. The plan included two nationwide campaigns using monovalent oral polio vaccine type 2 (mOPV2) covering all 18 states. The campaigns were conducted in November 2020 and January 2021 and reached over 8 million children under 5 years old in each of the 2 rounds. The outbreak was declared over in August 2022, after the Outbreak Response Assessment (OBRA) was conducted on 1 August 2022.
According to the WHO-UNICEF 2021 estimates of national immunization coverage in Sudan, the oral poliovirus vaccine third dose (OPV3) and inactivated poliovirus vaccine first dose (IPV 1) coverages were 85% and 94% respectively. On 18 December 2022, the Sudanese IHR National Focal Point notified WHO of the detection of cVDPV2 in one case, which was confirmed on 16 December. The case was for a child with acute flaccid paralysis (AFP), with onset of paralysis on 31 October, from West Darfur,
Western Sudan. Two stool specimens were collected on 10 and 12 November 2022. The isolate has undergone 38 nucleotide changes. The isolated virus is most closely related to the strain that circulated in Borno state,
Nigeria, in 2021, and is unrelated to the cVDPV2 strain that caused an outbreak in Sudan in 2020. On 1 January, cVDPV2 positive environmental sample were reported from West Darfur province, Genena district, with specimen collection date on 28 November 2022.
A field investigation was conducted, and a risk assessment is currently ongoing by local and national public health authorities, supported by partners of the Global Polio Eradication Initiative, and an outbreak response is planned.
WHO advice all countries, in particular those with frequent travel and contacts with polioaffected countries and areas, to strengthen surveillance for AFP cases and commence planned expansion of environmental surveillance in order to rapidly detect any new virus importation and to facilitate a rapid response.
Countries, territories and areas should also maintain uniformly high routine immunization coverage at the district level to minimize the consequences of any new virus introduction.
WHO does not recommend any travel and trade restrictions to Sudan based on the information available for this current event.
WHO’s International Travel and Health recommends that all travellers to polio-affected areas be fully vaccinated against polio. Residents (and visitors for more than 4 weeks) from infected areas should receive an additional dose of oral polio vaccine or inactivated polio vaccine within four weeks to 12 months of travel.

Source: World Health Organization