Nigeria is one of the three remaining polio endemic countries on the planet with Afghanistan and Pakistan being the others. The African nation reported 53 wild poliovirus-1 cases in 2013, while so far in 2014, only 5 cases have been reported.
However, what Nigeria is experiencing is an increase in circulating vaccine-derived poliovirus type 2 (cVDPV2), recording four cases during the past week and 18 cases total in 2014. Three of the cases were reported from Kano and one from Borno. The most recent cVDPV2 case had onset of paralysis on 22 June, from Kano.
The Global Polio Eradication Initiative (GPEI) says Vaccine-derived polioviruses (VDPVs) are rare strains of poliovirus that have genetically mutated from the strain contained in the oral polio vaccine.
The oral polio vaccine contains a live, attenuated (weakened) vaccine-virus. When a child is vaccinated, the weakened vaccine-virus replicates in the intestine and enters into the bloodstream, triggering a protective immune response in the child. Like wild poliovirus, the child excretes the vaccine-virus for a period of six to eight weeks. Importantly, as it is excreted, some of the vaccine-virus may no longer be the same as the original vaccine-virus as it has genetically altered during replication. This is called a vaccine-derived poliovirus.
The GPEI says that VDPVs will be seen populations that are seriously under-immunized. In situations like this, there are enough susceptible children for the excreted vaccine-derived polioviruses to begin circulating in the community. If a population is fully immunized against polio, it will be protected against the spread of both wild and vaccine strains of poliovirus. For more infectious disease news and information, visit and “like” the Infectious Disease News Facebook page