Status: co-affected by wild poliovirus type 1 (WPV1) and circulating vaccine-derived poliovirus type 2 (cVDPV2)
Following confirmation of WPV1 in May 2022, the Government of Malawi declared this outbreak to be a national public health emergency. The country is co-infected with WPV1 and cVDPV2.
Genomic sequencing analysis indicates that the detected WPV1 is linked to a strain that had been circulating in Pakistan in 2019, similar to a WPV1 case reported in Malawi in February.
Detection of the WPV1 in Mozambique confirms ongoing WPV1 transmissions in the sub-region. Mozambique has been actively participating in the multi-country emergency outbreak response implemented across the sub-region in response to the detected WPV1 in Malawi, alongside Tanzania, Zambia and Zimbabwe to reach more than 23 million children across the region during at least four multi-country emergency outbreak response campaigns. Two rounds of bivalent OPV have already been implemented, the most recent at end-April, with more than 4.2 million children vaccinated in Mozambique. At the same time, response in the country to the cVDPV2 outbreak is also ongoing.
National and subnational authorities continue to be supported by partners of the Global Polio Eradication Initiative, notably by experts of the African Rapid Response Team and the GPLN.
Detection of this most recent case underscores the appropriateness of the large-scale, rapid, multi-country emergency outbreak response across south-east Africa, in line with revised international polio outbreak response SOPs. The overriding priority is to continue to implement the subregional emergency response, by continuing to conduct large-scale, rapid and high-quality response campaigns.
WHO considers there to be a continued high risk of international spread of this WPV1, particularly across the south-east subregion of Africa, due to persisting subnational immunity and surveillance gaps and large-scale population movements. The risk is magnified by decreased immunization rates related to the ongoing COVID-19 pandemic.
Risk of spread associated with the cVDPV2 is currently deemed as moderate – historical and epidemiological evidence suggests WPVs have a significantly higher propensity for geographic spread than cVDPVs. However, full and high-quality outbreak response to both strains is urgently necessary, as both strains have the capacity to cause paralytic disease in children (with priority to address the WPV1 outbreak, given this strain’s higher propensity for causing paralytic disease and geographic disease).
It is important that all countries, in particular those with frequent travels and contacts with polio-affected countries and areas, 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.
International Health Regulations
As per the advice of an Emergency Committee convened under the International Health Regulations (2005), the risk of 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, ensure the vaccination of residents and long-term visitors and restrict at the point of departure travel of individuals, who have not been vaccinated or cannot prove the vaccination status.
The latest epidemiological information on WPVs and cVDPVs is updated on a weekly basis.
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 OPV or IPV within 4 weeks to 12 months of travel.