While the smoking man blames Primrose and Violet teams for creating the virus, the scientist makes an accusation of her own, vaguely stating, ' When it happened. Moreover, it's implied in the World Beyond post-credits scene that the researchers had no intention of releasing the virus and infecting the world, hinting the virus somehow wriggled its way out. shortly before the outbreak, it's possible other countries were involved in the study too, rather than France alone shouldering the blame.
Since Primrose team had traveled to the U.S. According to the smoking man, the facility housed numerous teams (he mentions Violet team and Primrose team) that worked on a project that ultimately became the TWD zombie origins.
From these two huge clues, only one possible conclusion can be drawn - The Walking Dead zombie apocalypse finds its roots in a French laboratory.