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Circulating vaccine-derived poliovirus type 2 – Sudan


On 9 August 2020, the Federal Ministry of Health, Sudan notified WHO of the detection of a circulating vaccine-derived poliovirus type 2 (cVDPV2) in the country. According to the notification, the virus is genetically-linked with Chad (sequencing results showed 12 to 19 nucleotide changes). Two Acute Flaccid Paralysis (AFP) cases were notified. The first case, a child of 48 months, had onset of paralysis on 7 March 2020 and was from Sulbi city of Kas locality in South Darfur state. The state is in the west of the country, bordering Central African Republic, South Sudan and close to the border with Chad. The second case, a child of 36 months, had onset of paralysis on 1 April 2020 and was from Shari city of AI Gedarif locality in Gedarif state in the east, close to the border with Eritrea and Ethiopia. Both children received the their last bOPV ( type 1 & 3) dose in 2019. Initial investigation indicates these cases are linked to cVDPV2s from the CHA-NDJ-1 emergence group which was first detected in October 2019 and is currently circulating in Chad and Cameroon. Eleven additional suspected cases have also been confirmed as cVDPV2 and field investigation reports are being consolidated. These cases are in the following states – Red Sea, West Darfur, East Darfur, White Nile, River Nile and Gezira. Hence, between 9 August and 26 August 2020, there have been a total of 13 cVDPV2 cases reported. Additionally, three cVDPV2-positive environmental samples from Soba, Elgoz and Hawasha sites from Khartoum were detected (samples collected on 29 March 2020). Sequencing of viruses isolated in Sudan so far reflects that the viruses are related with viruses reported earlier in neighboring Chad from where there were multiple separate introductions into Sudan from Chad. There is local circulation in Sudan and continued sharing of transmission with Chad.

Public health response

Following the detection of cVDPV2 in the country, the following response activities are being planned and/or implemented:

  • The Acting Federal Minister of Health declared a cVDPV2 outbreak in Sudan to the Cabinet within eight hours on Day Zero of outbreak (9 August 2020);

  • The Ministry of Health, supported by Global Polio Eradication Initiative (GPEI) partners, implemented a full field investigation, and started implementation of polio outbreak preparedness and response plan from Day Zero;

  • A national task force for outbreak response with representation from WHO and UNICEF has been established, Federal Epidemiological Team finalized Terms of Reference and composition of National Technical Committee for cVDPV2 outbreak control and convened first meeting on 9 August 2020;

  • Undersecretary of Health is chairing the steering committee for outbreak response, and the first meeting was convened on 9 August 2020;

  • Federal Epidemiological Team advised state epidemiological managers of South Darfur and Al Gedarif and other states with cases to activate the state’s emergency committee and start implementation of polio outbreak preparedness and response plan;

  • Response is coordinated with other departments such as health promotion and health emergencies; and cross-border coordination with neighbouring countries is being initiated.

WHO risk assessment

WHO assesses the risk of further international spread of cVDPV2 across central Africa and the Horn of Africa to be high. With large-scale population movements with other areas of central Africa and the Horn of Africa. A more thorough region-wide risk assessment is being conducted by the polio program. Across the African continent, 172 type 2 cases in 14 countries have been reported in 2020.

WHO advice

It is important that all countries, in particular those with frequent travel and contacts with polio-affected countries and areas, strengthen surveillance for Acuter Flaccid Paralysis 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’s International Travel and Health recommends that all travelers to polio-affected areas be fully vaccinated against polio. Residents (and visitors for more than 4 weeks) from polio-affected areas should receive an additional dose of OPV or inactivated polio vaccine (IPV) within 4 weeks to 12 months of travel.

As per the advice of an Emergency Committee convened under the International Health Regulations (2005), efforts to limit the international spread of poliovirus remains a Public Health Emergency of International Concern (PHEIC). Countries affected by poliovirus transmission are subject to Temporary Recommendations. To comply with the Temporary Recommendations issued under the PHEIC, any country infected by poliovirus should declare the outbreak as a national public health emergency and consider vaccination of all international travelers who live or visited the country for four weeks or longer. Countries infected by cVDPV2 should encourage residents and long-term visitors to receive a dose of IPV four weeks to 12 months prior to international travel.


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