The 28 year-old, who had lost one and drawn for of his 23 bouts coming into the contest, ended Fortuna’s 30-bout undefeated record in the eleventh round.
Sosa stalked the champion into the corner before unleashing a barrage of shots to drop Fortuna, who was insufficiently recovered, in the referee’s opinion, as he rose to his feet at the count of eight.
In the co-feature, Nehomar Cermeno regained the world title six years on from his reign as WBA bantamweight belt to become a two-weight world champion at the higher 122 pound limit.
The Venezuelan halted Jun Qiu Xiao with two minutes to go in the fight but was comfortably ahead on all three scorecards at the time of the stoppage.
In Nanning, British heavyweight Ian Lewison was successful in his first trip outside the UK with a second round knockout of Zhi Yu Wu at the Guangxi Sports Center Gymnasium.
Lewison proved too strong for Wu, who was fighting for only the fourth time in nine years, and ended the fight – along with the home fighter’s perfect record – with a crushing body attack.
With the triumph, 34 year-old Lewison picked up the vacant WBO Asia Pacific heavyweight title, a decent ranking with the organisation, and improved his record to 12-2-1.