Recently, there has been new cases of Circulating Vaccine-Derived Polio Virus 2 (cVDPV2) reported in the Manono and the Ankoro districts of in the Democratic Republic of Congo where the onset dates where November 9th and November 17th (one reported case in each) according to the Global Polio Eradication Initiative (GPEI). There had been no cVDPV2 cases for months now, and for the year, the total number of cases of cVDPV2 in the Democratic Republic of Congo has now reached 12 cases, which will probably be the number for the year considering how close this year is to ending (about time). So how exactly do cVDVs occur in the first place? Well, in the DNC, oral polio virus vaccine made from a weak live-attenuated vaccine is used where the virus replicates in the intestines. In the intestines, the poliovirus is excreted for 6-8 weeks, and during that time, some of the excreted virus may not be the same as the vaccine poliovirus. What ends up happening is that this new vaccine-derived poliovirus, if given the right environment where a population has immunization rates that are low, the vaccine-derived poliovirus can circulate, mutate, and potentially retain its original neurovirulence. These polioviruses that have reobtained their pathogenicity are the cVDPVs.
Additionally, the GPEI has made a report this week regarding wild poliovirus 1 in Pakistan. As a side note, the three remaining countries where wild-type poliovirus is still endemic around the globe are Pakistan, Afghanistan, and Nigeria. This case took place in the Kila Abdullah district, where the total number of WPV1 cases in Pakistan have now reached 8 cases for 2017, where the total number of cases for the year is now 20.