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The risk of global spread of poliovirus remains a public health emergency of international concern, a World Health Organization committee has found after looking into updates from 10 countries. While the risk of global spread of wild poliovirus remains, the risk of circulating vaccine-derived ones is higher.
Several measures like declaring poliovirus transmission as a national public health emergency and ensuring vaccinations for travellers and residents have been recommended by WHO.
The 34th meeting of the emergency committee under the International Health Regulations, 2005, on the international spread of poliovirus was convened by the WHO director-general on January 25, 2023.
The panel reviewed the data on wild poliovirus (WPV1) and circulating vaccine-derived polioviruses (cVDPV) for the global target of WPV eradication and cessation of cVDPV2 outbreaks by the end of 2023.
Details from Afghanistan, Botswana, Canada, the Democratic Republic of the Congo, Indonesia, Madagascar, Nigeria, Pakistan, Sudan and Zambia were looked into.
Several countries reported climate-related disasters, including both flooding and drought, that were causing greater vulnerability to several disease outbreaks, including polio. The ongoing conflict in several polio-affected countries also continued to pose significant challenges to the programmes.
An increase in wild poliovirus cases in 2022 shows the fragility of the fight against the highly infectious viral disease, a commentary published in BMJ Global Health journal in December said.
Despite the ongoing decline in cVDPV2 cases and the number of lineages circulating, the risk of the international spread of cVDPV2 remains high, WHO said.
Evidence of this includes the high transmission in DR Congo spreading to southern Africa (Zambia and Botswana). Spread from Chad to Sudan and from Yemen to Djibouti and Somalia were also noted.
The committee noted that much of the risk for cVDPV outbreaks could be linked to inaccessibility, insecurity, a high concentration of zero-dose children and population displacement. These have been most evident in northern Yemen, northern Nigeria, south-central Somalia and eastern DR Congo.
However, the successful introduction of the novel oral polio vaccine and re-introduction of the trivalent oral polio vaccine (tOPV) are expected to mitigate the risk of the international spread of cVDPV2.
There remain only three genetic clusters of WPV1 internationally — a cluster in Pakistan, one in Afghanistan and one in Africa. There has been no confirmed case of WPV1 in Pakistan since September 15, 2022 and in Afghanistan since August 29, 2022.
In Africa, there have been four cases of WPV1 in Mozambique, with the most recent in Tête province in Mozambique on August 10 2022. No further cases have occurred in Malawi since the single index case, with onset in November 2021.