Challenges associated with the recent outbreaks of wild-type Poliovirus in previously polio-free countries

During the last five years, outbreaks of wild-type polio infections following importation of wild-type poliovirus were reported from 39 countries that had been polio-free previously. The contributions through different host genetic profiles and/or any upsurge in neurovirulence of imported isolates might have been crucial for the sudden outburst of disease. For example, such profiles of adults with either a laboratory-confirmed/clinical or non-polio acute flaccid paralysis during the 2010 outbreak of wild poliovirus in the Republic of Congo might have contributed toward their increased susceptibility to wild poliovirus. During the two outbreaks of paralytic poliomyelitis in a vaccine-protected infant population in the Gaza Strip in 1974 and 1976, the frequency of histocompatibility leukocyte antigen (HLA) antigens in 58 of the affected children was compared with 113 control vaccinated subjects. HLA-AW19 and -B7 were found more frequently in the affected children. This difference, although not statistically significant, was consistent with the possibility that patients with paralytic disease had an HLA genetic makeup that was different from the rest of the population. Furthermore, following a single epidemic of paralytic poliomyelitis in 17 families in the Netherlands, different genetic factors encoded by the HLA complex influencing resistance to poliomyelitis were studied, including the pattern of inheritance of HLA haplotypes within the affected families. Whereas none of 17 other polymorphic markers deviated from the expected Mendelian pattern of inheritance, the inheritance pattern of HLA haplotypes was different in sib pairs consisting of a patient with paralytic poliomyelitis and a non-paralytic control sib. A significantly reduced amount of sharing of HLA haplotypes was observed than would have been expected by chance alone (p = 0.014). The sharing of HLA haplotypes between patients with non-paralytic poliomyelitis and healthy controls did not deviate significantly from the expected value, which suggested that HLA-encoded genetic factors may control resistance to the paralytic form of poliomyelitis. In Pointe Noire, Republic of Congo, 80% polio cases and an 82% fatality rate were recorded in those aged ≥ 15 y. The in vitro Challenges associated with the recent outbreaks of wild-type Poliovirus in previously polio-free countries