of the weakened poliovirus that was initially included in oral polio vaccine (OPV) and that has changed over time and behaves more like the wild or naturally occurring virus; this means it can be spread more easily to people who are unvaccinated against polio and who come in contact with the stool or respiratory secretions, such as from a sneeze, of an “infected” person who received oral polio vaccine; the CDC recommends that before any international travel, anyone unvaccinated, incompletely vaccinated, or with an unknown polio vaccination status should complete the routine polio vaccine series; before travel to any high-risk destination, CDC recommends that adults who previously completed the full, routine polio vaccine series receive a single, lifetime booster dose of polio vaccine References Society of the Republic of the Congo