Laboratory tests rule out the presence of wild and vaccine-derived poliovirus in the case of acute flaccid paralysis in Venezuela

Washington, DC, June 15, 2018 (PAHO/WHO) -Tests carried out by the specialized global laboratory for genetic sequencing have ruled out the presence of both wild poliovirus and vaccine-derived poliovirus (VDPV). The latter- VDPV- is a Sabin virus with genetic mutations that give it the ability to produce the disease. There is no risk of spread to the community or outbreaks of polio from this case.

An epidemiological update from the Pan American Health Organization (PAHO) published today reported that a 34-month-old boy had an onset of symptoms of acute flaccid paralysis (AFP) on April 29,2018. This child lives in a community with low vaccination coverage in the Orinoco Delta of Delta Amacuro State. A Sabin type 3 polio virus had been initially isolated from the child’s stool samples.

The global reference laboratory confirmed the presence of a Sabin type 3 virus. Isolation of Sabin type 3 poliovirus is possible in children and communities immunized with oral bivalent polio vaccine, which contains attenuated (weakened) type 1 and type 3 Sabin strains.

A number of different causes and diseases can lead to AFP, poliovirus being just one of them. In rare cases, the vaccine virus could be associated with paralysis. As part of global polio surveillance efforts, more than 100,000 cases of AFP are detected and investigated worldwide each year.

The child is being further evaluated clinically to determine alternative causes of paralysis. The final classification of the case of acute flaccid paralysis [to define whether or not it is associated with the vaccine] will be based on clinical and virological criteria assessed at 60 days after the onset of paralysis.

PAHO calls on countries to maintain strong surveillance together with high polio vaccination coverage in all communities, in order to minimize the risk and consequences of any eventual reintroduction or reappearance of poliovirus. PAHO and the partners of the Global Polio Eradication Initiative (GPEI) will continue to support local and national public health authorities in these efforts.