Evolving epidemiology of poliovirus serotype 2 following withdrawal of the serotype 2 oral poliovirus vaccine

Although there have been no cases of serotype 2 wild poliovirus for more than 20 years, transmission of serotype 2 vaccine-derived poliovirus (VDPV2) and associated paralytic cases in several continents represent a threat to eradication. The withdrawal of the serotype 2 component of oral poliovirus vaccine (OPV2) was implemented in April 2016 to stop VDPV2 emergence and secure eradication of all serotype 2 poliovirus. Globally, children born after this date have limited immunity to prevent transmission. Using a statistical model, we estimated the emergence date and source of VDPV2s detected between May 2016 and November 2019. Outbreak response campaigns with monovalent OPV2 are the only available method to induce immunity to prevent transmission. Yet our analysis shows that using monovalent OPV2 is generating more paralytic VDPV2 outbreaks with the potential for establishing endemic transmission. A novel OPV2, for which two candidates are currently in clinical trials, is urgently required, together with a contingency strategy if this vaccine does not materialize or perform as anticipated.

Epstein-Barr virus genotypes in NPC biopsies from north Africa

The genotypes of Epstein-Barr virus (EBV) were investigated in North African nasopharyngeal carcinoma (NPC) biopsies, nasopharyngeal chronic inflammation (NCI) biopsies, and saliva of healthy individuals from Algeria and Tunisia where there is an intermediate incidence of NPC. The prevalence of A-type virus in NPC, NCI biopsies and saliva of healthy individuals was found in these regions by means of a PCR assay. Restriction enzyme polymorphism analysis by Southern blotting revealed that all North African EBV variants have a conserved restriction site on BamHI W'-I' and XhoI LMP gene. No additional BamHI enzyme site on the BamHI-F fragment was observed; however, the presence of an extra BamHI site on the BamHI-H fragment giving 2 HI and H2 fragment-like EBV M-ABA strains was found. All EBV strains present in NPC or NCI biopsies at all ages were homogeneous in these polymorphisms and no correlation was observed between the EBV genotypes from NPC patients and clinical stages of the cancer. These characteristics revealed a significant difference between the EBV variants common in Chinese NPC and those in North African NPC.