Importation and outbreak of wild polioviruses from 2000 to 2014 and interruption of transmission in Cameroon

Background: Efficient implementation of the global eradication strategies consisting of Acute Flaccid Paralysis (AFP) surveillance and mass immunization campaigns led to interruption of indigenous wild poliovirus transmission in Cameroon in 1999. Objectives: This study describes type 1 and type 3 wild poliovirus (WPV) importation, incidence, geographic distribution and control since the original interruption of transmission in Cameroon. Study design: Stool samples from AFP patients under the age of 15 years in Cameroon were collected nationwide and subjected to virus isolation on RD and L2OB cell cultures. Resulting virus isolates were typed by intratypic differentiation (ITD) and analysis of the VP1 coding sequence of the viral genome. Surveillance data originating from Cameroon between 2000 and 2014 were considered for retrospective descriptive analyses. Results: From 2003 to 2009, multiple WPV importation events from neighboring countries affected mainly in the northern regions of Cameroon but did not led to sustained local transmission. Throughout this period, 16 WPV1 and 5 WPV3 were detected and identified as members of multiple clusters within type specific West Africa B genotypes (WEAF-B). In 2013-2014, a polio outbreak associated to a highly evolved ("orphan") WPV1 affected four southern regions of Cameroon. Conclusions: The appearance of highly evolved lineage of type 1 WPV suggests potential surveillance gap and underscore the need to maintain comprehensive polio immunization activities and sensitive surveillance systems in place as long as any country in the world remains endemic for WPV. (C) 2016 Elsevier B.V. All rights reserved.