Outbreak in summary:
On May 15, 2022, a case of wild poliovirus type 1 (WPV1) was reported in Mozambique through the Global Polio Laboratory Network (GPLN). Genomic sequencing analysis results indicate that the current isolate of WPV1 is genetically linked to a strain detected in Pakistan in 2019 and similar to a case of WPV1 reported in Malawi in February 2022.
As part of response measures following confirmation of the case in Malawi, two rounds of bivalent oral poliovirus vaccine (bOPV) campaigns were carried out in the country, with more than 4.5 million children vaccinated.
The risk of international spread, particularly in southeastern Africa, remains high, owing to the persistence of suboptimal immunity and surveillance gaps and large-scale population movements.
On 15 May 2022, the GPLN reported confirmation of a case of wild poliovirus type 1 (WPV1) in Mozambique. The case is a 12-year-old girl with acute flaccid paralysis (AFP), with onset of paralysis on March 25, from Changara district, Tête province on the border with Zimbabwe and Malawi. Two stool samples were collected for testing on April 1 and April 2. On May 14, the samples were confirmed as WPV1 by the National Institute of Communicable Diseases (NICD) in South Africa. The child had previously received three doses of bivalent oral poliovirus vaccine (bOPV) but no inactivated poliovirus vaccine (IPV). Genomic sequencing analysis indicates that the newly confirmed case is linked to a strain that was circulating in Pakistan in 2019, similar to a case of WPV1 reported in Malawi in February 2022 (for more details on this case, see the news on disease outbreak published March 3, 2022). The last indigenous case of wild poliovirus in Mozambique was reported in 1993.
Mozambique is also affected by a concurrent outbreak of circulating vaccine-derived poliovirus type 2 (cVDPV2), with seven cases reported in the country since 2021, the most recent on March 25, 2022.
According to the WHO-UNICEF national immunization coverage estimate, coverage of the third dose of oral poliovirus vaccine (OPV3) and the first dose of inactivated poliovirus vaccine (IPV1) was 73% and 78%, respectively, in Mozambique in 2020.
Figure: 1: Countries reporting WPV1 cases and neighboring countries implementing preparedness plans
Epidemiology of Poliomyelitis
Poliomyelitis (polio) is a highly infectious viral disease that primarily affects children under the age of five. The virus is transmitted from person to person and spread mainly by the fecal-oral route or, less frequently, by a common vehicle (e.g. contaminated water or food) and multiplies in the intestine, from where it can invade the nervous system and cause paralysis. . The virus is transmitted by infected people (usually children) through faeces, where it can spread quickly, especially in areas with poor hygiene and sanitation systems.
The incubation period is usually 7 to 10 days, but can range from 4 to 35 days. Up to 90% of those infected are asymptomatic or have mild symptoms and the disease is usually not recognized. In mildly symptomatic cases, initial symptoms include fever, fatigue, headache, vomiting, stiff neck and limb pain. These symptoms usually last from 2 to 10 days and most recovery is complete in almost all cases. However, in the remaining 10% of cases, the virus causes paralysis, usually of the legs, which is most often permanent. Paralysis can occur as quickly as a few hours after infection. Of cases with paralysis, 5-10% die when their respiratory muscles become immobilized.
Two of the three types of wild poliovirus have been eradicated (WPV2 and WPV3), with global efforts underway to eradicate WPV1. Currently, wild poliovirus is endemic in two countries: Pakistan and Afghanistan. The detection of WPV1 outside of these two countries where the disease is endemic demonstrates the continued risk of international spread of the disease until all corners of the world are free of WPV1.
There is no cure for polio; can only be prevented by immunization.
public health response
Mozambique has been actively participating in the multi-country emergency outbreak response implemented across the South East Africa region in response to the WPV1 case reported in Malawi in February 2022, along with Tanzania, Zambia and Zimbabwe to reach over 23 million of children around the world. region. Two rounds of bivalent OPV vaccination campaigns have already been implemented, the most recent at the end of April, with more than 4.5 million children vaccinated in Mozambique. At the same time, the in-country response to the cVDPV2 outbreak is also ongoing.
National and sub-national authorities continue to be supported by Global Polio Eradication Initiative (GPEI) partners, including experts from the African Rapid Response Team, GPLN, UNICEF and local organizations. Surveillance throughout the sub-region continues to be strengthened.
The detection of the current case underscores the need for a large-scale, rapid, multi-country emergency outbreak response across Southeast Africa, according to Revised international POPs in response to polio outbreaks. The main priority is to continue to implement the sub-regional emergency response, continuing to carry out large-scale, rapid and high-quality response campaigns.
WHO risk assessment
The detection of one case of WPV1 in Mozambique, and the second case in the Southeast Africa region, confirms ongoing WPV1 transmissions in the sub-region.
WHO considers that there is a continuing high risk of international spread of WPV1, particularly in the South East Africa sub-region, due to the persistence of suboptimal national immunity and surveillance gaps and large-scale population movements. The risk is even greater due to the decrease in the immunization rate related to the ongoing COVID-19 pandemic.
The risk of spread associated with the concurrent outbreak of cVDPV2 is currently assessed as moderate due to historical and epidemiological evidence suggesting that WPVs have a significantly greater propensity for geographic spread than cVDPVs. However, a comprehensive response to the outbreak of both strains is urgently being implemented as both strains have the ability to cause paralytic disease in children.
It is important that all countries, particularly those with frequent travel and contact with polio-affected countries and areas, strengthen surveillance for AFP cases and begin planned expansion of environmental surveillance to quickly detect any importation of new virus and facilitate a response. fast. Countries, territories and areas should also maintain uniformly high routine vaccination coverage at the district level to minimize the consequences of any new virus introduction.
WHO International Travel and Health recommends that all travelers to polio-affected areas be fully vaccinated against polio. Residents (and visitors longer than four weeks) of affected areas must receive an additional dose of OPV or IPV within four weeks to 12 months of travel.
On the advice of a 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 fulfill the Temporary recommendations issued under the PHEICany poliovirus-infected country must declare the outbreak a national public health emergency, ensure vaccination of residents and long-term visitors, and restrict at point of departure travel by individuals who have not been vaccinated or cannot prove vaccination status.
Latest epidemiological information on WPVs and cVDPVs is updated weekly in the GPEI location on the Internet.
WHO does not recommend any restrictions on travel and/or trade to Mozambique based on the information available for this current event.