Who spread the parasitic virus in resident evil 5?

Wesker, a mysterious organization, obtained the samples of Plagas dominant species captured by Ada in Biochemical 4, and artificially modified the samples to cultivate Plagas type 2 (centipede vine) and type 3 (spherical beetle). And use this as a bargaining chip in exchange for Tricell's trust and full cooperation to help him complete the Uroboros project of cleaning human beings.

During Biochemical 5, BSAA learned about a case of biological weapons trading in a certain place in West Africa, and came to investigate and stop it. This transaction was made by Irwin, Tricell's biological weapons agent. At the same time, Wesker and Exela Ghioni (CEO of Tricell1West Africa Branch) tested the new parasite Plagas Type 2&: Type3 weapon, so he asked Irwin to walk the parasite.

However, the parasites of the aborigines of Dubai Tribe began to spread from the last study.