Mutated Vaccination Virus Causing Paralysis in First Syrian Polio Outbreak in Years

A recently confirmed polio outbreak in Syria is connected to low levels of vaccination, worsened by conflict. It is the first confirmed incidence of polio in Syria since 2014. Before 2013, the last case of polio in Syria was in 1999.

The new cases occurred in Deir-Ez-Zor governorate in Syria. The strain was isolated on April 25, from two people who were infected and one uninfected contact. Paralysis began in the two cases on March 5 and May 6. The cases are of a circulating vaccine-derived poliovirus type 2 (cVDPV2).

Circulating VDPDs like this one arise from mutations in the oral polio vaccine within under-vaccinated populations. The vaccine contains a weakened version of the polio virus that does not typically cause illness, but when it has the opportunity to circulate longer than usual in an under-vaccinated population, more genetic changes can occur and make it into a dangerous form that can paralyze.

According to the Global Polio Eradication Initiative (GPEI):

Although access to Deir-Ez-Zor is compromised due to insecurity, the Governorate has been partially reached by several vaccination campaigns against polio and other vaccine-preventable diseases since the beginning of 2016. Most recently, two campaigns have been conducted in March and April 2017 using bivalent oral polio vaccine (OPV). However, only limited coverage was possible through these campaigns.

The GPEI is connected to the World Health Organization (WHO), other partners, and national governments.

Michel Zaffran, Director of Polio at WHO, said, "There are very difficult situations and access issues in this governate of Deir-Ez-Zor where this outbreak is occurring. This makes it very hard, and sometimes extremely hard, and sometimes extremely dangerous, to vaccinate and quickly increase the immunity of children in these areas."

An initial risk assessment has found "solid levels" of disease surveillance and low population immunity rates. Outbreak response plans are being finalized and include targeted vaccination campaigns. Searches are being conducted for additional cases, and surveillance and immunization are being stepped up in countries neighboring Syria as well.

The polio cases in 2014 were from a wild poliovirus type 1 strain, and unrelated to the current outbreak. Similar strategies will be used in combating this cVDPV type 2.

People's access to vaccines in Syria can depend on coordination between health organizations and local authorities, which may be complicated by the unstable political situation on the ground. Armed conflict continues, and when it prevents the population from accessing resources like health care, the consequences add to the danger from direct violence.

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Cover image by Meredith Boyter Newlove and James Archer/CDC