Summary of poliovirus circulation in 2016 – Pakistan
In Pakistan, a circulating vaccine-derived poliovirus type 2 (cVDPV2) has been detected from environmental samples in Quetta, Balochistan. Two isolates with apparent genetic linkages were isolated from environmental samples, collected on 20 October and 28 November 2016. Virus was isolated from environmental samples only and no associated cases of paralysis linked to the isolated strains have been detected in Quetta or anywhere else in the province.
Pakistan also continues to be affected by endemic transmission of wild poliovirus type 1 (WPV1). As of 21 December, 19 WPV1 cases have been reported in 2016. It is the lowest number of annual cases ever reported, from the fewest number of affected areas in the country.
The majority of the polio cases during the last six months were reported from non-reservoir areas, i.e. from ‘tier 2, 3 and 4’ districts (districts which are considered to be more vulnerable to polio re-infection). There have been no paralytic cases of wild poliovirus from the traditional polio reservoirs in Pakistan since February 2016.
Public health response
A response with monovalent oral polio vaccine type 2 (mOPV2) in the Quetta and neighbouring districts is now planned, in line with internationally-agreed protocols. The first campaign of a series of campaigns is planned for 2 January 2017. In addition, the Ministry of National Health Services, Regulations and Coordination (MoHSRC), supported by World Health Organization (WHO), UNICEF and other partners, is further strengthening active search for cases of acute flaccid paralysis (AFP), and conducting an in-depth field investigation to more clearly ascertain the circulation of this strain. Pakistan continues to implement the National Emergency Action Plan for polio eradication, to urgently interrupt all remaining strains of polio transmission in the country.
The area affected by the reported type 2 virus is part of a transnational common reservoir for WPV1 that extends into Southern Afghanistan. Interrupting WPV1 transmission in this area remains the top most priority of the federal, provincial and district health teams. Meticulous preparations are underway through the national and provincial Emergency Operations Centres (EOCs) and District Polio Control Rooms for high quality implementation of upcoming back-to-back national and sub-national vaccination rounds, in December 2016, January 2017 and February 2017 using bivalent oral polio vaccine (bOPV). These campaigns are critical to addressing the remaining pockets of under-immunized populations sustaining low-intensity WPV1 transmission within the common reservoir.
To ensure high quality, preparations are focusing on allocating adequate resources to the highest-risk areas; tailoring operational plans to identified reasons for missed children; validating vaccination teams’ microplans, vaccinator selection, training and supervision; and enhancing local engagement with communities through community leaders. In order to jointly address transmission across the common reservoir, close coordination is ongoing with Afghanistan teams at all levels.
WHO risk assessment
WHO assesses the risk of international spread of WPV1 within the common reservoir between Pakistan and Afghanistan to be high (due to the historical spread of such strains across the joint epidemiological block with Afghanistan). WHO also assesses the risk of spread of cVDPV2 within the common reservoir as medium to high. Risk of international spread of WPV1 or cVDPV2 to other countries is assessed low.
It is important that all countries, in particular those with frequent travel and contacts with polio-affected countries and areas, strengthen surveillance for acute flaccid paralysis (AFP) cases 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 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 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 is 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 travellers. Any country that exports poliovirus should ensure vaccination of all international travellers before departure.